Juicy, delicious mangos are one of my favorite tropical fruits.
Mango trees have been around for about 50 million years. This means mangos were around for the mass extinction of the Cretaceous Era, through the extreme climate changes and carbon cycling seen at the end of the Paleocene Era, and again today. Hopefully, mangos will continue to thrive.
Native to South Asia, mangos (Mangifera indica) were part of the spice trade of the 15th and 16th centuries. They were brought to the colonies in the 17th century but, because refrigeration was unavailable, those mangos were pickled. Due to poor communication, other pickled foods, such as sweet peppers, were also referred to as mangos. For a time, the word mango was a verb that meant “to pickle”. But I digress.
Types of mangos
You may be surprised to learn that there are over 500 mango cultivars. In commercial mango orchards, these cultivars are often interplanted to improve pollination. The current market leader is the ‘Tommy Atkins’ variety, due to its nice appearance, productivity, disease resistance, and shelf life. Other, less resilient cultivars, such as ‘Alphonso’, are said to provide better eating enjoyment. With so many cultivars to choose from, home growers can afford to be picky. And those mangos you buy in the store? Many of them (like many other fruits) are picked unripe, so they will never attain the rich flavor of a tree-ripened mango. These climatic fruits do continue ripening after leaving the parent plant, but their flavor is never quite what it could have been. [Keep in mind, when you buy mangos at the store, each fruit is picked by hand, then washed, polished, and stickered by people working in warehouses.]
The mango tree
Mangos are stone fruits, right along with apricots and cherries. And that large flat seed - it’s a drupe. Like legumes, pineapple, sorghum, and sweet potatoes, mangos have evolved alongside a helpful bacteria (Gluconacetobacter diazotrophicus) that fixes atmospheric nitrogen, making it available to to the plant and its neighbors, until it goes to seed.
Mango trees are big. When I say big, I mean that they can reach heights of over 130 feet. The crown can be 30 feet across and these trees can produce fruit for more than 300 years. [For comparison, the standard, commercially grown nectarine tree is only expected to produce fruit for 15 years.]
Before you let that size scare you off, know that most commercially grown mango trees are pruned to more manageable sizes, and you can, too.
Mango trees have an extensive root system. They produce a taproot that may go down 20 feet and abundant feeder roots that spread out both horizontally and vertically.
Mangos are evergreen trees with large, broad leaves that start out orangish-pink, and then turn dark shiny red before maturing to dark green. Mangos produce small, white, fragrant flowers in clusters, called panicles. These flowers are pollinated by insects, but it is estimated that less than 1% of the flowers produced by a mango tree will every mature to form a fruit. It takes 4 to 5 months to go from flower to harvestable fruit. And you know that red blush on mango fruit? It has nothing to do with ripeness or sweetness. Instead, it is an indicator of how much sun that side of the fruit was exposed to as it grew.
Inside that delicious fruit is a drupe that fights being removed with every fiber of its being. The reason for this is because mangos, along with avocados, lychees, and cocoa seeds cannot tolerate being dried out or too cold. This type of seed is called recalcitrant. Recalcitrant seeds, also known as unorthodox seeds, lose their viability when stored. Other orthodox seeds can tolerate varying degrees of cold, dryness, and storage time. [Note, the stories about seeds from King Tut’s tomb germinating are bogus.] If you want to grow a mango tree from a pit, your odds will improve significantly if you start it right away. Most commercially grown mango cultivars and bare root stock are grafted onto sturdy rootstock.
Before you start growing your own mango tree, you may want to find out if you are sensitive to the oils found in mango stems, sap, and leaves. Some people are sensitive, while others can be severely allergic. Also, mango trees are killed by extended exposure to temperatures below 30°F. If your microclimate receives substantial frost, you may need to protect your tree in winter. If you enjoy snowy winters, you may want to try growing a dwarf mango indoors and pollinating it by hand.
Commercially grown mango trees are often girdled by professionals to increase the sugar content of the fruit, but I advise against this practice, as it can kill your mango tree if done incorrectly.
Mango pests and diseases
Sadly, mango trees are susceptible to a wide variety of pests and diseases. This list is so long that I encourage you to skip it (unless you are really into this sort of thing). If you own a mango tree, you should familiarize yourself with each of these conditions and their treatments.
According to Wikipedia, bacterial diseases of mango include bacterial fruit rot, crown gall, and bacterial canker. Fungal diseases of mango include alternaria leaf spot, anthracnose, black banded disease, black mildew, black mold rot, black rot, blossom blight, blue mold, branch canker, branch necrosis, ceratocystis wilt, charcoal fruit rot, charcoal root rot, crown rot, crusty leaf spot, curvularia blight, felt fungus, fruit rot, galls, grey leaf spot, hendersonia rot, leaf blight, leaf spot, macrophoma rot, fusarium dieback, mucor rot, mushroom root rot, phoma blight, phyllosticta leaf spot, pink disease, powdery mildew, Rhizopus soft rot, various root rots and seed rots, scab, sclerotinia rot, shoestring rot, sooty blotch, sooty molds, stem canker, stem end rot, stem gall, stemphylium rot, stigma leaf spot, tip dieback, transit rot, trunk rot, twig blight, verticillium wilt, white sooty blotch, wood rot, and various forms of dieback. Fixed copper sprays are the most common treatment for many of these fungal diseases.
If that weren’t enough, dagger, lance, and sheathed nematodes, vine mealybugs, guava fruit flies, Mexican fruit flies, melon flies, polyphagous shothole borers, and Oriental fruit flies will attack mango trees, as will an algae that causes red rust, along with a parasitic lichen. Copper, zinc, and boron deficiencies can also cause problems, while too much nitrogen combined with not enough calcium can cause a condition known as soft nose. It’s a wonder we get mangos at all!
Mangos, like most other tropical fruits, produce significant amounts of ethylene gas, a ripening agent. If you need to speed ripen an avocado for guacamole, put it in a paper bag with a mango.
Did you know that mangos are related to cashews?
Now you know.
Indoors or out, you can create an attractive salad garden that provides fresh, crisp salads practically year round.
Imagine walking over to a container, raised bed, or garden patch with a pair of scissors and snipping off fresh ingredients for a salad. Much like an herb garden, salad gardens can provide a variety of colors and textures to your landscape, balcony, or home, as well as delicious, fresh ingredients for your meals.
Where can you grow a salad garden?
Balconies, patios, raised beds, windowsills, towers, and containers are all the space you need to create a salad garden. You can also add salad plants in with your other plantings!
You can use a collection of artistic planter pots, or some of those long, narrow planting containers found at yard sales and thrift stores, or you can get really creative, using takeout containers, an old wheelbarrow, or any other food safe container. And that’s really important. Be sure that whatever container you choose is rated for food use - many pallets are sprayed with a cocktail of chemicals, and some ceramic pots are decorated with toxic enamels. Once you’ve made sure your containers are food safe, it’s time to start choosing your plants!
Choosing plants for a salad garden
Start your salad garden plant selection with foods you and your family will eat and enjoy. There’s no sense using up valuable growing space on plants you don’t want. To select the best plants for your salad garden, consider the time of year each plant will be able to grow in your area. Check with your local County Extension Office and read those seed packets. You can also get all the information you need right here, online. If you will be growing outdoors, be sure to check with the USDA Hardiness Zone Map to identify your zone. You will also want to identify which plants are perennial, which are annuals, and which are biennials:
Salad perennials — chives, patience dock, Malabar spinach, nasturtiums, perennial rocket, sorrel [If you have the space, rhubarb and artichokes provide HUGE, ongoing crops each year]
Salad biennials — kale, parsley, Swiss chard
Salad annuals -- arugula, bok choy, cilantro, dill, lettuces, mizuna, radish, spinach
The perennial plants will serve as year-round anchors in your salad garden, the biennials may take 2 or 3 years before going to seed, and annuals will have to be replaced each year. Or, maybe they won’t. We will get to that in a moment.
One tool for helping in the garden design planning process is to get a package of 3x5 index cards and create a card for each type of plant, putting all the relevant growing information on the card. That information would include:
You can spread the cards out on a table and move them around, to create attractive, productive groupings that will play well together. Consider the height and shape of each plant. A deep container that features tall, wispy dill in the center, offset by brilliantly colored Swiss chard, surrounded by a bright green halo of short, mounding lettuces will look lovely and taste good! Keep a lookout for hybrid dwarf varieties of many salad greens that fit better in containers. If you are growing indoors, you may need to add grow lights during winter.
As your salad garden begins to produce edibles, remember to continue planting new annual seeds every 2 to 4 weeks, whenever the growing conditions are appropriate for each plant. This succession planting will keep you in salad greens practically year round. The important thing about planting a salad garden is to keep planting those seeds!
Surprises in the salad garden
Some plants don’t seem to play be the rules of botany. Beets, for example, are classified as biennials. This means they are ‘supposed’ to generate a fleshy root in the first growing season, to store nutrients for the next growing season, during which seeds are produced. [By the way, beet seed-bearing stems are lovely - they look like Japanese art.] My seed-producing beets, however, have been providing me with beet leaves and seeds for over 5 years now! I use the seeds to grow new plants, and the baby beet leaves are delicious in salads.
You can add a tiny touch of art to your salad garden with ceramic bunnies, glass balls, or tiny metal snails. Will these features help your plants grow? No, they won’t. But they might make you smile!
Harvesting your salad garden
Many salad greens can be harvested using a cut-and-come-again method. This mean you remove outer leaves, as you need them, and the plant simply generates new leaves from its center.
If you allow some of your annual and biennial salad garden plants to complete their lifecycle, going to seed, you will end up with a perpetual motion salad garden that continues to generate new edible plants each year.
While most salad greens prefer cooler temperatures, if you plan around your microclimate, you might be able to put together a salad garden that will continue producing throughout most of the year.
What do you put in your salads?
Stumperies are not Gordian Knots of the pop-quiz world. Instead, stumperies are garden features that use large branches and tree trunks as their anchor points.
While visiting the Missouri Botanical Garden, I was delighted to discover an entire section of the gardens dedicated to stumperies. Coming around a curve in the path, I was met with a cool, green peaceful bit of gardening that featured logs, branches, sheets of bark, tree trunks, and skyward bound tree roots, surrounded by wispy ferns, colorful lichens, and fuzzy mosses. The effect was soothing and peaceful - and who doesn’t need more of that these days?
Originally described as a “Victorian horticultural oddity”, stumperies use branches and other large pieces of tree to create habitat for a wide variety of shade-loving plants, growing them more closely together than might otherwise be possible. First created in 1865 England, stumperies often use storm-damaged or diseased trees to create a unique shade gardening space, rather than going to the trouble of disposing of those trees.
Personally, I had an ancient apricot tree whose trunk had been regularly sprayed with a sprinkler for years before we bought the property. Rot had taken over the tree and the root system was pretty much nonexistent. Rather than waiting for it to fall over on somebody, we tipped it over and moved it to a corner of the yard, where it now serves as a new growing space and a good place to sit.
Stumperies are based on what naturally occurs in a forest. As a tree ages, it eventually falls. When it does, it slowly decomposes, absorbing rain water, improving nearby soil structure, and acting as a ‘nurse log’ to plants that have adapted to growing on rotting wood. To design your own stumpery, you must look at each piece of wood and bark as an artistic component. Try different arrangements until you have achieved something you like. Don’t worry, there are no wrong answers. Here are some tips to creating a healthy stumpery:
Plants used in stumperies
The most common plants found in stumperies are mosses, ferns, and lichens. Hostas, hellebores, epimedium, rhododendrons, bleeding hearts, and some bulbs can also thrive in a stumpery.
You can encourage moss growth on logs and stones by smearing them with yogurt [or that carton of soured milk from the back of the fridge]. You can also install shade-loving edibles, such as arugula, basil, blueberries, bok choy, celery, chervil, chives, cilantro, fenugreek, garlic, ginger, kale, lettuces, Malabar and other spinach, mint, mustards, nasturtiums, onion, parsley, potatoes, raspberries, sorrel, tarragon, and tomatillos. The perennials will continue indefinitely, and you can allow some of the annuals to go through their full lifecycle and propagate themselves!
Benefits of stumperies
Stumperies create micro habitats for local flora and fauna, increasing your garden’s biodiversity. Beetles, toads, and lizards often find sanctuary in all the hidden nooks and crannies provided by a stumpery. Of course, slugs and snails and other pests do, as well. But birds enjoy the extra perches and snacks, so it all balances out.
Stumperies can be a good way to put old wood to work in the garden. They can hide eyesores, make use of neglected corners, and create a whimsical woodland that adds some tranquility to your day. If you don’t have stumps readily available, you can always contact local arborists and construction companies. Very often, they will be happy to provide you with all the material you need for free. [That way, they don’t have to pay to dispose of such large items.] Which reminds me: keep in mind that, eventually, the trees and branches that make up your stumpery will disappear and need to be replaced.
After writing this post, I think I will have to create a more formal stumpery with my apricot trunk. I’ll keep you posted.
While it might be fun to imagine tiny worms wearing hardhats and utility belts, there's nothing cute about carpenterworms.
Carpenterworms (Prionoxystus robiniae) are the larval form of a common moth, and they love to burrow into apricot and pear trees. They can also be found in many ornamental trees, such as maple, oak, birch, cottonwood, ash, and willow. Once these pests are inside your trees, they can be difficult to evict.
As you can see, this is a robust caterpillar. They can be 1/2 an inch in diameter and 2 to 3 inches long. They have a dark, brownish head and a yellowish white body that is covered with fine hairs. They have sharp, hooked legs on the middle section (thorax) and distinct fleshy legs on the abdomen
Damage caused by carpenterworms
These wood-boring insects live in galleries, feeding on sapwood. Knowing the signs of infestation can help you get a handle on this pest before the damage becomes irreversible. The galleries created by carpenterworm feeding tend to be vertical, except for the entrance. These entrances are often found in branch crotches and in bark crevices. Tunnels are 1/2 an inch in diameter and 6 to 10 inches long. This tunneling creates points of entry for many other pests and diseases. Adult female carpenterworms seem to prefer areas that are already infested for egg laying, which can result in multiple galleries in the same area of the same tree. All that feeding and tunneling can weaken branches, making them more likely to break in strong winds, or when supporting heavy crops. Branches can also become girdled by carpenterworm feeding and tunneling, and die.
Adult carpenterworms are large, mottled grey moths that can have a 3-inch wingspan. Their coloration blends with tree bark and lichen. This camouflage makes them difficult to see. If you are able to catch one and spread out its wings, you wing be able to see if you have a male, with orange hind wings, or a female, with off-white hind wings.
Because adult female carpenter moths cannot fly very far, they tend to lay their eggs near the gallery where they were feeding. Three to six eggs are laid in the crevices near an existing gallery entrance. Upon hatching, the larvae immediate start boring into the sapwood, leaving small, rectangular entrance holes.
As they feed, the larvae will occasionally push sawdust and frass (bug poop) out of the ever-widening entry. The larvae will feed on the sapwood and hardwood until they reach maturity, molting 8 to 31 times over the next 2 to 4 years. Finally, mature pupae wriggle their pudgy selves to the entry hole and create a protective pupal case, which will block the hole until adult moths emerge. In California, this usually occurs May through July. As soon as adults start flying, they mate and the cycle continues.
Signs of carpenterworm infestation
The first sign of carpenterworm infestation is stained areas on the trunk. These stains are a combination of sap, sawdust, and frass. You may also see pupal cases sticking 2/3rds of the way out of the tree. Since the stained areas and branch dieback may also be caused by clearwing moths/currant borers, flatheaded borers, bark beetles, and longhorned borers, it is important to identify the pest before trying to control the problem.
Healthy trees are better able to protect themselves, so start by planting trees in the right location, at the proper depth, with regular fertilization and irrigation.
Because these caterpillars are already protected by the tree, insecticides do not work. There are a couple of specific nematodes, Steinernema feltiae or S. carpocapsae, that have been very successful at controlling carpenterworm larvae. Before you place your order, however, make sure that these are exactly the type of beneficial nematodes you are buying. Any other variety will be ineffective against carpenterworms. And be sure to follow the package directions exactly, or you will have wasted your money.
Small infestations can sometimes be controlled by poking long, sharp, flexible wires into the galleries and skewering the caterpillars. This is tricky because you really can’t see if you killed them or not. The only way to really know is to clear all the frass and other debris away from the area and mark the spot with some paint. Then, check the area every week for signs of frass. If frass and sawdust are seen, you missed and the caterpillar is still alive and busy feeding and burrowing.
Heavy infestations are dangerous and should be left to a professional arborist. This is because tree branches that are compromised this badly are very likely to fall on you. Since none of us are exempt from the laws of physics, and heavy branches can paralyze or kill you, stay away from them, and call an expert.
This winter, take a few minutes each week to inspect your trees for signs of frass and sawdust, or pupal cases, and cut those cute little, hardhat wearing pests off at the knees.
Glass snails, such as this whimsical piece by GlassBorisov, are a delightful way to add art and color to houseplants and your garden.
The same is generally not true of real snails. Yesterday morning, after our first rain of the year, I noticed a snail trail. Snail trails are pretty normal in most gardens, but this one ended with a flat-bodied snail I’d never seen before.
Introducing, the glass-snail family (Oxychilidae). Glass-snails get their name because their shells are translucent. Looking closely at my discovery, I could see the snail body through the shell!
Glass-snails are land snails that breathe air. Unlike marine snails, which breath using a single gill, land snails have evolved a single, simple lung. Most glass-snails are omnivores. They eat everything: live plants, dead plants, dead animals, insects, poop, other slugs and snails (and their eggs), sowbugs, and earthworms.
Sorting out glass snails
Specific characteristics are used when comparing different snail species, including height, width, number of whorls, and the umbilicus. The umbilicus is the snail’s bellybutton. It is the tiny opening at the center of the whorls on the underside of the snail’s shell.
Only three glass snails are found in California, at this time: cellar snails, garlic snails, and Drapernaud’s snail. [I'm not sure if my guest is a cellar or Drapernaud's glass-snail, but I'll keep you posted.]
Cellar glass-snails (Oxychilus cellarius) have shiny, translucent yellowish-brown shells are just under 1/2 an inch wide, 1/6 of an inch tall, with 5-1/2 to 6 whorls. The umbilicus is very narrow. The snail itself is bluish-grey, with small brown freckles and a groove that runs along each side of the foot
The garlic glass-snail (Oxychilus alliarius) gets its Latin name, a twist on the onion family (Allium), because they emit a garlic odor when disturbed. Originally from the Netherlands, Great Britain, Ireland, Poland, and the Czech Republic, the garlic snail has spread its range to include Columbia, Latvia, and California. Garlic snails are reddish or greenish brown, and the snail is blackish blue. The shell is 1/4 of an inch in diameter, a little more than 1/8 of an inch high, with 4 or 4-1/2 slightly convex whorls. The umbilicus is 1/6 of the overall diameter, and the whorls are coiled more narrowly than cellar glass-snails.
Drapernaud’s glass-snail (Oxychilus draparnaudi) is larger than the other glass snails, being slightly more than 1/2 an inch in diameter, and the shell is a waxy yellowish-brown on top and somewhat lighter underneath. The body is a dark blue and grey color. Drapernaud’s glass-snail is carnivorous.
How to control snails
Unless you are enjoying artistic versions of this common pest, managing snails is an ongoing task. It comes as no surprise that these snails’ peak breeding season in the Bay Area is autumn, just before our rainy season begins.
The first step in snail management is to inspect and quarantine new plants. A single snail can lay over 400 eggs. Putting new plants into isolation for a couple of days, with a beer trap nearby, can prevent years of frustration. Once infestation occurs, try to reduce hiding places, such as boards, stones, and other debris. Regularly applying slug and snail bait, and using beer traps, can take a big bite out of the snail population, before they start taking bites out of your plants. Going outside with a flashlight at night, you can catch them feeding - handpick them and feed them to your chickens or dispose of them in the trash.
Did you know that snails have a powerful sense of smell?
Now you know.
Growing up in Southern California, I was lucky enough to attend a childcare program that was built on the grounds of a former walnut grove. Scattered throughout the property, there were dozens of ancient walnut trees, great for climbing, tire swings, and more delicious walnuts than any of us kids could possibly have eaten. But we sure tried!
People have been growing walnut trees longer than any other food tree. Nearly 10,000 years ago, in ancient Persia, walnuts were grown for members of the royal family. Traded along the Silk Road, and then via sea trade, Persian walnuts made their way to Rome, where they were called Jupiter’s royal acorn, and to England, where the name was changed to English walnuts, even though they were not being grown commercially in England at that time. In the 1700s, missionaries brought walnuts to California.
Types of walnut trees
There are actually several different trees that qualify as walnut. They are all members of the Juglans genus. The familiar English walnut is only one of four types of walnut tree:
The walnut tree
Walnut is a deciduous hardwood. It is also one of the few trees with a true taproot. [Most tree roots are fibrous.] Walnut trees can take 5 or 6 years before they produce fruit. When selecting a site for a walnut tree, keep in mind that a mature walnut tree can reach 40 to 80 feet, in both height and width, and it can live 50 to 250 years!
Walnut trees, like avocado trees, are monoecious, which means they produce both male and female flowers. Male walnut flowers are catkins that look like hanging cat tails. The female flowers are spiky and short. If you slice open a walnut twig, you will see a series of tan chambers, called pith. This is different from the white pith found in citrus rinds.
Fruits of the walnut tree
Unlike chestnuts, which are both botanical and culinary nuts, the common walnut isn’t a nut at all. You may be surprised to learn that walnuts are actually a type of stone fruit. [I know! I was surprised, too!] This means that the walnuts you enjoy eating are a form of fleshy fruit, known as a drupe. Almonds are also drupes. Surrounded by a thick, green rind, the walnuts you see in the grocery store are not what they look like when they are still hanging in the tree. That rind is actually the fruit of a walnut tree, but you wouldn’t want to eat it. It’s nasty.
Walnut trees, like citrus and many other fruit and nut trees, tend to produce heavy crops one year and a light crop the following year. Known as alternate bearing, these fluctuations allow trees to recover from heavy production years.
You have probably heard that walnut trees put out toxins that make it impossible to grow other plants nearby. This is only partly true. Many plants use a type of chemical warfare, called allelopathy, to reduce competition. Walnut trees produce do produce toxins that can cause some other plants to wilt. Tomatoes, potatoes, eggplant, peppers, blackberries, raspberries, blueberries, and asparagus do not grow well when planted near a black walnut tree, according to the University of Illinois Extension. At the same time, according to the PennState Extension, onions, beets, squash, melons, carrots, parsnips, beans, yarrow, stonecrops, and corn can all be grown near a walnut tree without any problems. In fact, in commercial walnut groves, a type of agroforestry, called alley cropping, is used to plant other crops, such as corn, between the rows of walnut trees.
Propagating walnut trees
While you can certainly buy a bare root walnut tree, there are other ways. You can plant a raw walnut in the ground, or, if you know of someone with a walnut tree, you can use air layering. Layering is a form of vegetative propagation. Strawberry runners are an example of layering. The nice thing about air layering is that the parent plant continues to feed and care for the newly developing plant, since they are still attached to one another. To air layer a walnut, pull a stem down until it touches the ground at what would have been a leaf node. Instead of developing into a leaf, that bud will start putting out roots.
Walnut trees can produce nuts on the same spurs for several years. Because of this, mature walnut trees do not require renewal pruning. The only pruning needed is occasionally thinning branches to maintain overall shape and good health. Young walnut trees are trained using the modified central leader system. In this method, a single, strong shoot is encouraged up the central line of the tree. Two or three lateral branches, spread evenly around the tree, both vertically and horizontally, are allowed to grow. All other branches are removed. Eventually, there can be five to seven lateral branches in place before the central leader is removed.
Walnut pests and diseases
Walnuts are susceptible to an astounding number of pests and diseases. Luckily, walnuts are rugged trees that rarely need assistance in fighting off these foes. It’s still a good idea to know what your tree might be up against. Many varieties of scale insects, including walnut scale, frosted scale, European fruit lecanium scale, San Jose scale, Kuno scale, and Italian pear scale may be found on walnut. Walnut husk flies, aphids, southern fire ants, walnut twig beetles, fall webworms, Pacific flathead borers, navel orangeworms, false chinch bugs, redhumped caterpillars, American plum borers, and Mediterranean fruit flies prefer walnut, as do tortricid moths, such as the light brown apple moth, which can cause leaf roll of walnut. A type of eriophyid mite, called the blister mite, will also attack walnut trees, as will European red mites and webspinning spider mites. Codling moth larvae will burrow into the nut meat of English walnuts, starting in April. You can monitor your trees for many of these pests by using pheromone traps.
Diseases, such as crown gall and walnut blight can be prevented and treated with Bordeaux mixture or fixed copper. Walnut trees may also become infected with anthracnose, armillaria root rot, phytophthora root and crown rot, branch wilt, and several canker diseases. If that weren’t trouble enough, squirrels, voles, pocket gophers, rats, and deer will try to get at as much of your walnut crop as they can.
While many trees are treated with horticultural oils during dormancy, oils should not be used on walnut. Dormant oils are phytotoxic (poisonous) to walnut trees. Like apricot trees, walnut trees are also susceptible to Eutypa dieback. This fungal disease can kill a tree. The easiest way to avoid it is to only prune your walnut tree during summer, when there are no rains expected. Also, make sure that your sprinklers are not hitting the tree’s trunk.
Walnuts contain high levels of oils that can turn rancid. To keep walnut meats fresh, they are left in their shells and placed in cold storage. If you buy walnuts from a store and plan on using them within one month, store them in your refrigerator. Since walnuts can absorb odors, be sure to keep them away from fragrant foods, such as cabbage, broccoli, and fish. Longer storage should be done in the freezer.
Walnut trees can make a magnificent addition to your foodscape, providing decades of delicious nuts and welcoming shade from the summer sun.
Hugelkultur is a no-dig gardening method that uses mounds of logs and branches covered with soil to create growing space. Mounds are commonly used when growing pumpkins, melons, and other cucurbits. These “hills” help prevent waterlogged roots, prone to rot. Hugelkultur is something entirely different.
These mounds start out 3 feet high and wide. As decomposition occurs, the mounds collapse. After being built, mounds are normally left to rest for several months, though some people plant them right away. Since more decomposition is occurring during the first seasons of a hugelkultur’s life, heavy feeding crops, such as melons, squashes, cabbages, potatoes, and tomatoes are grown first, followed by less demanding crops, such as beans, strawberries, and peas, in later seasons. The average lifespan of a hugelkultur is 5 to 6 years.
Hugelkultur beds are generally positioned so is to be perpendicular to prevailing winds and slopes. For a more whimsical appearance, you can create hugelkultur in whatever shape suits your fancy, such as spirals or mazes. While enthusiasts claim hugelkultur can be used to redirect stormwater, these mounds do not have the strength or stability required of solid earthworks. Instead of protecting against flooding, hugelkulturs can cause even more destruction as floating logs and branches join the water flow.
Problems with hugelkultur
Before you get caught up in the hugelkultur fad, understand that there is, as far as I know, no scientific research to verify the claims made by hugelkultur fans. This doesn't mean the claims are false. It simply means that scientific studies have not yet verified the claims. There are some obvious problems, however.
Traditionally, hugelkulturs were recommended for counteracting “poisoned layers” of soil. This is a terrible idea. Plant roots will move through the mound and into the soil below. Using raised beds with soil barriers, or container gardening, are much better solutions.
Hugelkultur is also said to feed and water nearby plants. In nature, fallen logs do provide water and nutrients to nearby plants. This occurs because they are on top of the soil. As they decompose, they become more porous, storing water and releasing nutrients. These ‘nursery logs’ have long been a source of water and nutrition for young trees and other plants. Hugelkultur logs are underground and do not function in the same way.What is hugelkultur?
Hugelkultur was started in Germany as a way to put woody debris to good use when, at the time, it was illegal to burn it. While proponents state that hugelkultur started “hundreds of years ago”, there is no proof to substantiate that claim. The term was first used in 1962 by Herrman Andrä, a German gardener, when he noted the diversity of plants growing on a pile of woody debris at his grandmother’s home. Andrä and others standardized the method, claiming that the rounded mounds increased growing area and nutrient availability, while storing moisture for growing plants.
How to build a hugelkultur bed
At first, hugelkultur was nothing more than long piles of logs, branches, twigs, and plant waste, such as straw, compost, or sod, covered with soil. In some cases, the design evolved to start with a dug trench or sunken area. The soil removed to make the trench is then used on top of the mound, before planting occurs. The trench method is more commonly used in sandy soils [In another method I found, cardboard, kitchen waste, and old clothing are also incorporated into the mound. Depending on the type of fabric, cotton and wool, as opposed to polyester and rayon, this may or may not be a good idea, respectively.]
Other concerns about hugelkultur include the potential for nutrient deficiencies or toxicities. With all that decomposition going on, nitrogen deficiencies may occur. This can happen because the microorganisms responsible for breaking down plant materials use nitrogen as an energy source. (See nitrogen cycle) On the flip side, so much organic material is being used and broken down that nutrient levels can become excessive, creating toxicities within the soil and groundwater.
Also, the materials used to create the mounds can cause problems of their own. Cedar and walnut contain chemicals that slow the growth of other plants. Some branches, such as Chinese privet, will generate roots all along the buried branches and twigs, and take over the area. Because there is sod, water, soil, and nutrients available in a hugelkultur, weeds can also become a serious problem.
If hugelkultur works for you, wonderful! If you haven’t tried it yet, you may want to put all those logs, stumps, or tree trunks to work in the garden in other ways. Larger pieces make attractive stumperies, while logs make excellent path markers. Ultimately, these woody limbs will break down, adding nutrients and improving soil structure but, as nature intended, these things take time.
Small, red delta pheromone traps (if you can find them) may also be used in April through June, depending on where you live. Check your trap every 2 weeks through November. The California Extension Office has an excellent male vine mealybug identification information sheet.
Mealybugs have been around for a long time. There is a relatively new, invasive mealybug that may be attacking your grapes.
Traditionally, California grape growers have had to watch for grape mealybugs, obscure mealybugs, and long-tailed mealybugs. These species generally do not cause significant problems, as long as their populations do not get out of hand. They are easy to recognize because of the clusters of grey, soft-bodied females gathering on the underside of leaves and in nooks and crannies. The invasive vine mealybug is another problem altogether.
Vine mealybugs (Planococcus ficus) are native to the Mediterranean areas of North and South Africa and Europe. Vine mealybugs were first seen in California in the mid-1990s and had spread to 17 California counties by 2011. Vine mealybugs are now considered a significant pest of grapes, figs, avocado, apple, bananas, mango, citrus, date palm, and several ornamental plants.
Vine mealybugs are difficult to see because they spend most of their lives protected under the bark, on roots, and around developing buds. Only during spring, when they become active again, can you sometimes see them moving away from the roots and trunk and into the leaf canopy. By summer, vine mealybugs may be found under the bark of first- and second-year canes, among fruit clusters, and under leaves. Sometimes, ants can be seen providing the mealybugs with transportation to their summer feeding grounds.
Vine mealybug description
Vine mealybug females are 1/8 of an inch long, pink, oval-shaped, and covered with a white, mealy wax that also covers filaments (spines) along the sides and posterior end. These filaments are shorter than those seen on other mealybugs, and there are no long tail filaments. Like their cousins, vine mealybugs have a segmented body. Males are tiny, winged, and you’ll probably never see them, unless you have a 30x microscope. They are 0.7 inches long, amber colored, with beaded antennae, one pair of wings, and 4 tail filaments that may stick together. It is important to know which mealybugs you are dealing with. If you see mealybugs, try to collect some and place them in a sealed plastic bag, or in a container of alcohol, and take them to your local County Extension Office for identification. This also helps authorities better understand the spread of this invasive pest.
Vine mealybug lifecycle
In summer, females lay 300 to 700 eggs in the leaves above the fruit in little pouches, called ovisacs. First instar nymphs, called crawlers, are orange and very tiny. During winter, only nymphs are present. They can be found hiding under the bark around the graft union, below the base of spurs, and around pruning wounds. There can be 3 to 7 generations a year.
How to control vine mealybugs
Being an invasive pest, vine mealybugs do not have as a many natural predators as their native cousins. Because vine mealybugs are such a serious threat to California grape growers, parasites of these particular mealybugs have been released in the state. This has helped somewhat, but eradication appears to be impossible at this point. Since these beneficial insects are unavailable to the home grower, the best things you can do to protect your vines is to inspect them regularly, especially during spring, monitor and control ant traffic with sticky barriers, and to quarantine new vines and other plants before installing them. Also, sanitize your tools regularly. Vine mealybugs also feed on burclover, malva, black nightshade, sowthistle and lambsquarters, so controlling these weeds can also help prevent infestation.
Damage caused by vine mealybugs
Vine mealybugs are phloem sap suckers that produce significantly more honeydew than native mealybugs. This honeydew attracts protective, disease-carrying ants and creates a growth medium for sooty mold on fruit clusters. These invasive pests can also carry grapevine leafroll viruses and corky bark disease. Vine mealybugs reproduce at a much faster rate than their native cousins.
Protecting your grapevine from vine mealybugs is an important step toward providing your family with fresh, delicious, organic, homegrown grapes.
Plant a chestnut tree today for decades of meaty, delicious nuts.
American chestnut trees are majestic. While young, the bark is a smooth, reddish-brown. As the tree matures, the bark becomes darker and deeply furrowed. Their mature height of over 100 feet equals 1/3rd of a football field. Try picturing that in your yard!
Cousin to beeches and oaks, the roasted chestnuts of holiday fare fame should not be confused with horse chestnuts, which are mildly poisonous, or water chestnuts, which are aquatic tubers. No, chestnuts, or Sardian nuts, as they were called in their native Asia Minor, or Jupiter’s nuts, from the Roman Empire, have been cultivated since 2,000 B.C., and they have a rich, delicious history.
Chestnuts as food
Brought to Europe by Alexander the Great and the Roman Empire, chestnut trees thrive in the Mediterranean climate, providing a high carbohydrate food to the masses. Unlike most other nuts, chestnuts are not particularly high in protein or fat. Nutritionally, they are closer to grain or potatoes than nuts, containing 40% carbohydrates.
Chestnuts were a primary food source for much of southern Europe, until the potato was introduced. From the 1500s through the 1700s, Genoan landowners were required to plant four trees each year: olive, fig, mulberry, and chestnut. As a result, that area has rich, productive forests and farmland. [Imagine how productive your yard could be if you plant 4 food-producing trees each year!]
Being high in calories and carbohydrates, chestnuts were often ground into a flour to make a type of flatbread [chestnut flour does not rise, as it does not contain gluten]. Unfortunately, this earned it a reputation as a poor man’s food, which lead to a decline in interest. This was unfortunate, because chestnuts are a highly nutritious food.
Across the pond, Native Americans enjoyed local chestnut species long before Europeans arrived. Regions of the Appalachian Mountains were fully one-fourth chestnut trees. Since a mature American chestnut tree can produce 50 to 100 pounds of fruit each year, that ends up being a lot of food.
There have been some impressive chestnut trees. The Tortworth Chestnut, also known as the Great Tree of Tortworth, found in South Gloucestershire, has been around since Stephen, King of England (1092-1154). This beast has a circumference of 50 feet! [If any of you have a photo of this tree, please share it in the Comments!] Even larger, the Hundred Horse Chestnut grows on Italy’s Mt. Etna and is believed to be the oldest living chestnut tree, at approximately 4,000 years.
There are 8 or 9 different deciduous trees and shrubs that are called the chestnuts. These are placed into one of four groups: American, Chinese, European, and Japanese, for obvious reasons. Each species has distinct characteristics.
European and American chestnuts tend to grow more tree-like, with a single erect trunk, while the Asian varieties tend to be multilayered and more spread out. Also, the former varieties offer stunning fall foliage. There are hundreds of chestnut varieties to choose from. UC Davis offers an excellent list of chestnut trees suitable for growing in California.
Like avocados, chestnuts have both male and female flowers. Chestnuts are not self-compatible, which means you will need at least two trees or shrubs to produce fruit. Flowers appear in late spring and early summer. Male (staminate) flowers are shaped like a cat’s tail and are called catkins. Catkins mature before the female flowers, and the pollen has a rich, sweet aroma. The female, fruit-producing (pistillate) flowers grow together in groups of 2 or 3, which end up forming a prickly, 4-lobed structure called a calybium. The calybium is what ultimately develops into the hull that protects the fruit. Pollen is moved predominantly by wind, though beneficial insects also perform some pollination.
The fruit of chestnut trees is held in sharp, pokey burrs, called cupules. These burrs tend to be clustered. The burrs of some varieties each contain one nut, while other varieties can hold up to severn. Burrs turn yellowish-brown and split open as the fruit matures. Each fruit has a pointed end, called a flame, and an attachment scar end, called the hilum. Chestnut fruit has two skins: the hard outer pericarpus, called the heel, and an attached, thinner skin, called the pellicle or episperm. Chestnuts are both culinary and botanical nuts, unlike almonds, peanuts, cashews, and walnuts.
Chestnut lumber is lovely, but larger pieces tend to split. Most chestnut lumber is now produced through coppicing. Young chestnut lumber is more durable than oak of the same age. Both species contain high levels of tannins. Chestnut wood was a common source of natural tannins for tanning leather.
How to grow chestnuts
Chestnuts are in high demand and the supply is limited. This keeps prices high, and is a good argument for growing your own (assuming you are not in a hurry). Going from bare root sapling to mature, productive tree takes about 10 years. Chestnuts need specific chilling hours to produce flowers and fruit. If the dormant period does not get cold enough, you will still have a beautiful tree, but no homegrown chestnuts. Also, if two chestnut trees are planted such that their canopies touch, they produce no fruit. We don’t know why.
Allowed to fall to the ground, chestnut seeds germinate right away. You can start them in a cold frame, container, or seedbed outdoors, where they will experience winter temperatures. Seedlings require protection from squirrels and other rodents.
Chestnut trees prefer full sun. They need good drainage and regular irrigation (31 inches per year). Once established, chestnuts are drought resistant. They do not grow well in heavy clay or alkaline soil. Chestnuts prefer a soil pH of 5.5 to 6.0. If you live in the Bay Area, where alkaline clay is pretty much the rule, don’t despair. Chestnut scions can be grafted onto oak rootstock! Chestnut trees are managed much the way walnut trees are grown. Chestnut trees should be trained into a modified central leader scaffold system for the best sun exposure and overall health.
Chestnut pests and diseases
Squirrels, rabbits, deer, wild boar, livestock, and birds can all take a bite out of your chestnut harvest. You may want to consider a tree cage, at least while the tree is small. Chestnut gall wasps (in southeastern states), some moths, the oak roller weevil, oak aphid, filbert worm, oak leaf mining moth, shot hole borers, and the chestnut weevil are common pests of chestnut, depending on where you live.
In 1904, some Asian chestnut trees that had been planted on Long Island, were found to be infected with chestnut blight (Cryphonectria parasitica, formerly Eudothia parasitica). Over the next 40 years, 4 billion chestnut trees died, nearly wiping out the American chestnut. Reforestation efforts, started in the 1930s, using seeds from the few remaining living stumps are giving this majestic tree a new lease on life, but it’s a slow process. There are now blight-resistant cultivars. Chestnut trees are also susceptible to Armillaria rot. On the other hand, chestnuts are believed to be naturally resistant to oak rot fungus. You can protect your chestnut tree against sunburn by whitewashing the trunk, and help it stay healthy by mulching under the canopy (but not touching the trunk).
Chestnuts have been candied, soaked in wine, and roasted as a holiday tradition throughout Europe for a very long time. To early Christians, chestnuts symbolized chastity, while in modern day Japan, they symbolize both good times (mastery) and bad times (strength).
You can roast your own chestnuts at home in the oven. Start with raw, unpeeled, chestnuts. Cut an X on the rounded bottom of each nut. Some people soak their chestnuts in water for 30 to 60 minutes before baking, others use wine, and still others don’t soak at all. You decide. If you do soak them in water, drain and pat dry before roasting.
Spread the nuts out on a baking sheet. Bake for at least 15 to 20 minutes, or until the skins have pulled away from the cuts and the nutmeats have softened. Take them out of the oven and let the nuts rest for a few minutes. Peel and eat!
Did you know that chestnuts are the only nuts that contain vitamin C?
Now you know.
Where are your tree’s roots? Are they deep-rooted or shallow-rooted? What difference does it make?
How much is root?
A single tree can have hundreds of miles of roots, and hundreds of thousands of root tips. Approximately 20% of a tree’s weight is found in the root system. That means an 80’ hardwood tree, with a 24 inch diameter, which weighs approximately 10 tons, can have 4,000 lbs. of roots. [Your average new car weighs 2,871 lbs.] That’s a lot of roots.
Function of tree roots
Tree roots serve several functions. They anchor the tree in place. Tree roots absorb and store water, oxygen, and nutrients from the soil, compete with neighboring plants, and maintain incredible relationships with beneficial fungi and bacteria found in the soil. You may not think of tree roots when it comes to photosynthesis, but you should. According to Thomas O. Perry, in a report published by the Harvard Arboretum, tree roots produce produce nitrogenous compounds that are essential to photosynthesis. Knowing what your trees’ roots are doing, and what they need, can help you keep your trees healthy and productive. But it all starts with the first root.
The first root
The first root that emerges from a tree seed, be it an acorn, peach pit, or pine nut, is called the radicle. The radicle nearly always grows straight down, pulled by gravity. Once the radicle is established in a place where it can absorb water, oxygen, and nutrients, further root development continues.
Taproots and oxygen
In some cases, such as walnuts, pines, and oaks, the taproot persists, growing down 3 to 6 feet. This taproot can grow extremely deep, under ideal conditions, but that's rare. Other trees develop a system of fibrous roots, and the taproot is not maintained. Tree roots move through the macropores and micropores found in the soil. If the soil is too hard or compacted, roots cannot move through it. Tree root growth generally stops when insufficient oxygen levels are encountered. This can be caused by compaction, the presence of hardpan, or by flooding. Cherry trees are particularly sensitive to insufficient oxygen in the soil, which is why they tend to be difficult to grow in compaction-prone clay. [Their roots contain chemicals that turn into cyanide gas when oxygen levels are too low! (Rowe and Catlin, 1971)]
The place where major roots emerge from the subterranean trunk is called the root collar. Most trees put out 4 to 11 major roots that grow horizontally from the root collar. These roots are generally found in the top 12 inches of soil, though they can range 3 to 7 feet deep, depending on age, species, and local conditions. These roots are can be 3 to 15 feet long, and up to 1 inch in diameter. Like trunks and branches, these woody, perennial roots develop growth rings, and they provide anchoring support from which all the transport roots emerge.
Transport roots normally fill a circular area that can be 4 to 7 times greater than the drip line. Transport roots do exactly what their name implies: they transport resources collected by the root hairs into the vascular bundles that feed the rest of the tree. To take good care of your trees, you really need to know where these roots might be.
GARDEN CHALLENGE: Where are your roots?
I challenge you to learn where your trees’ roots right be. You can do this outside, with a tape measure and a long rope, or you can do it on your computer, or with paper and pencil. However you do it, it will probably surprise you just how far these roots go. Regardless of the method you use, these steps will help you learn where your trees’ root might be:
Note how the root systems of all your trees (and large shrubs and everything else) overlap in significant ways. Also note where those root systems might end up covered by your house, the street, or some other dead zone. [Printouts of current satellite views of your property are very handy for activities like this one.]
But there is a lot more to tree roots than perennial and transport roots. There are some roots you’ve never seen, and some you’ve probably never even heard of!
In particularly dry, sandy soil, trees will put out striker roots. Striker roots grow straight down, from the perennial roots, until they encounter a barrier or insufficient oxygen. These striker roots, as well as taproots, then start branching out horizontally, creating an entirely new layer of root system.
Feeder roots are where all the action happens. These are the microscopic root hairs (which aren’t actually hairs at all) that interact with water, oxygen, and mineral molecules found in the soil, along with billions of soil microorganisms that make everything possible. These feeder roots grow upward into the top soil to collect (and disperse) nutrients, oxygen, and water.
Causes of tree root damage
You may be surprised to learn that fully 99% of a tree’s roots are found in the top 3 feet of soil, and that it is a lot easier than you might expect to damage those roots. Tree roots are frequently damaged by drought, flooding, extreme temperatures, the presence of rocks or hardpan, nematodes, springtails, and root-eating vermin, such as voles. Tree roots can also be damaged by human actions, even when our intentions are good. These actions include:
Signs of root damage
Tree roots can be seen as a reflection of the aboveground portion of the tree. Not necessarily in terms of size or shape, but in overall health. For example, if the leaves are repeatedly removed from a tree, some of the roots will die, as well. In the same way, if a portion of the root system is damaged or drowned, a corresponding dieback of the aboveground portion of the tree can be seen.
The vascular systems of some trees, such as oaks, are tied directly to branches on the same side of the tree. Damage to the roots will be reflected in poor health or death of branches on the same side of the tree. In other cases, portions of roots are tied to branches on the opposite side of the tree, while others have more of a spiral or zig-zag vascular system that serves the entire tree. These patterns can vary between species and individual trees, but arborists use this information to sort out problems related to irrigation, pesticides, fertilizers, insecticides, and herbicides.
Helping tree roots
You can help your trees’ roots stay healthy by aerating the soil, avoiding compaction, irrigating properly, mulching, and top dressing with organic material. These actions will help the worms, microorganisms, and other processes “fluff” the soil, improving soil structure, and provide important nutrients.
Unlike the crown shyness seen above ground, where the leaves of individual trees avoid touching, the root systems of different trees, shrubs, and other plants can intertwine in complex networks that are made evermore astounding when you learn how they use soil microorganisms to share nutrients and to communicate. [We’ll talk more about that later.] In situations where several of the same species of tree are growing near each other, the roots of one tree will graft to the roots of another tree. [I’ve said it before, I’ll say it again - the more I learn, the weirder the world gets!]
I hope that you can now see your trees with new eyes, eyes that can better imagine what is happening underground and under your feet.
Fragrant pine needles are modified leaves.
Unlike the soft, flat leaves of broadleaved plants, many evergreens have evolved an entirely different sort of leaf, the needle.
Most plants with needles need very little water, which means they are called xerophytes. These plants also tend to grow at higher elevations. Each tree produces millions of needles over the course of its life. The physiological characteristics of needles are an adaptation that allow evergreens to thrive where other plants would perish.
Benefits of needles
Conifer needles have many characteristics that allow them to hang on to the water absorbed by the roots:
The dark green color of most needles also aids in collecting the sun’s energy.
Anatomy of a needle
Even though needles look very different from classical leaves, they still have many of the same structures and functions. For example, needles perform photosynthesis. The stomata, used in gas exchanges and moisture level control, are arranged in lines, down the length of the needle, or in small patches.
Needles often grow in clusters, called fascicles. There are also single needle fascicles. The number of needles found in a single facile can help you identify the species. At the base of needles, you will see a sheath, called the fascicle sheath. This sheath can be persistent, as in hard pines, or deciduous, as with soft pines.
Most needle-bearing trees are evergreen, though there are a few deciduous species. Just as the leaves of deciduous trees change colors and fall in autumn, the needles of many evergreens also change color and fall, it’s just not as obvious. This is a natural occurrence, much like citrus June drop. Most evergreens hold onto their needles for 2 or 3 years. Discarded needles are usually those found closer to the trunk. If needles are lost elsewhere on the tree, or if needles are discolored, it can indicate fungal disease.
Needle pests and diseases
Pine wilt can also cause discolored needles. Pine wilt is caused by pinewood nematodes, which attack the vascular tissue. Pinewood nematodes move from tree to tree by catching a ride on pine sawyer beetles, in a behavior called phoresy.
Pine needles are a favorite food of some moth and butterfly species, as well as the pine sawfly. Goats will eat pine needles, too, but you wouldn’t want to drink the milk they produce after that snack. It’s nasty.
Acidic pine needles
There is a popular misconception that pine needles can be used to acidify soil. While it is true that fresh pine needles are slightly acidic, and a thick layer of needles on the ground can interfere with the growth of competing hardwoods, the dried needles, often called pine straw, are not acidic. While they will improve soil structure by adding organic material as they decompose, pine needles will not, I’m sorry to say, acidify your soil.
Pine needles can be steeped in boiling water for a refreshing tea that is high in vitamins A and C. Pine needles have long been used to make baskets, trays, and other crafts. Here is a pine needle basket made by my grandmother.
Native to South and Central America and the Caribbean, delicious guava fruits are the epitome of tropical flavor. But guava trees can become invasive. Are you up to the challenge?
Cousin to clove, allspice, eucalyptus, and evening primrose, guava trees (Psidium guajava) are a low maintenance, drought tolerant, highly productive tropical fruit tree. If you enjoy eating guavas, growing your own is certainly worth some thought.
Guava plant description
Guavas are an evergreen tree or shrub with shallow roots. Under ideal conditions, trees can reach 12 to 20 feet in height. Elsewhere, they remain more shrublike. Guavas grown in containers will remain small. Attractive, one inch flowers are white. Leaves are thick and fragrant. Fruits generally have green or yellow skin and white flesh, but there are cultivars with red skin, and pink or red flesh. Fruits can range in size from 2 to 5 inches in diameter.
Types of guava
There are many varieties and cultivars of guava. You may have heard of apple guava, strawberry guava, and pineapple guava. While the first two are actually guava varieties, pineapple guava is a different species altogether. In the world of guavas, plants are sorted by fruit skin and flesh color, skin thickness, and sweetness. To find the best variety for your microclimate, contact your local County Extension Office.
Guavas are extremely drought tolerant, but plants require up to 39 inches of water each year to produce a good crop. Feeding roots only go down 9 inches, so top dressing with aged compost is an excellent way to keep guava trees fed.
Guava pests and disease
Guava wood is naturally resistant to insects and fungal disease. They are, however, susceptible to attack by weevils, mites, and guava fruit flies, and they are a host to the Caribbean fruit fly. Many moth and butterfly caterpillars will also feed on guava leaves, and the Erwinia psidii bacteria can cause rot diseases.
Guavas contain a lot of pectin, so it is easy to make guava jams, jellies, and marmalades.
You’ve proba-bly never heard of proba bugs. They are another relatively new pest on the California scene. And they love artichokes.
Proba bugs (Proba californica) have been around for some time, but they used to prefer coyote brush. Coyote brush is a common native plant found along highways in agricultural areas of California. At some point (around 1997) a proba bug decided to give artichokes a try. From that moment on, proba bugs have become an increasing threat to artichoke plants. So, what do they look like?
Proba bug description
Adult proba bugs are plain brown and only 0.2 inches long. [That means you could line up 3-1/2 proba bugs across the top of a dime.] Nymphs start out looking like pale yellowish green aphids, except that they move a lot faster than aphids, due to their long legs. During the next to developmental stages (instars) they are reddish-brown, and then they develop light and dark bands on they abdominal area during the final two instars. [I couldn't find any usable photos of proba bug nymphs - sorry!]
Proba bug lifecycle
Proba bugs are active year round (just a lot slower in winter). As temperatures begin to rise, usually in March, they begin feeding and breeding in earnest. Eggs are laid on artichoke petioles (leaf stems) and hatch within 20 to 30 days. Nymphs go through five instars before reaching adulthood.
Damage caused by proba bugs
The damage caused by proba bugs is similar to that of lygus bugs, only proba bugs are more aggressive in their feeding habits. Adults and nymphs feed on young artichoke leaves and at the base of developing buds. They feed by piercing the tissue and injecting a toxin that kills plant cells. As the surrounding leaf tissue continues to grow, these punctured areas turn into brown dead spots that dry and fall off, leaving a shot hole appearance. Feeding on the base of flower buds causes the bud [the part we eat] to turn black. Not very appetizing. This phytotoxin also causes stunting and deformed flower buds. Severely affected leaves will be smaller than normal and chlorotic.
Controlling proba bugs
Until relatively recently, commercial artichoke fields were treated with organophosphates and chlorinated hydrocarbon insecticides. Use of these neurotoxins is being phased out, so proba bugs are becoming more of a problem. Infested fields can lose 20 to 30% of the harvest to proba bugs. Farmers are now removing the coyote brush near their fields and tilling the crop residue under, in a practice called stumping, to help combat this pest.
Natural predators, such as big-eyed bugs, damsel bugs, minute pirate bugs, and spiders all feed on the nymph stage of proba bugs, so avoid using broad spectrum pesticides.
You can help protect your artichoke plant by cutting the plant off at ground level, once flower production is done for the year, and monitoring for signs of infestation in March and April.
It is unusual for a new disease or pathogen to be discovered. It is even more rare when a new disease is found to be caused by a common pest. This is Fusarium dieback, and it can kill your trees.
Fusarium dieback is a fungal disease carried by invasive borers. As borers burrow into trees, they carry three different fungal pathogens with them. These fungi form colonies within a tree’s vascular system, blocking the flow of water and nutrients. Trees infected with Fusarium dieback must be destroyed and disposed of by professional arborists.
Symptoms of Fusarium dieback
Since this disease affects many different types of trees, and is caused by different fungi, it is no wonder that there are different symptoms. Infected avocado trees, for example, will exhibit sawdust-like frass (bug poop), gumming, and sugar volcanoes. Sugar volcanoes are white discharges of sugary sap. On other host trees, you may see dark, greasy looking areas on the bark, withered leaves and stem tips, and the presence of white mycelium under the bark. Mycelia are the vegetative growths of fungi.
As the infestation progresses, perfectly round, tiny borer entry and exit holes may become visible. These holes are only 0.03 inches in diameter, so you have to look very closely, usually just below areas showing symptoms of disease. Eventually, you will start seeing branches die. If you cut into an infected branch, you will see that the wood is discolored, brown or black. If you scrape the bark away from entry or exit holes, you will also see discoloration. After cutting, be sure to disinfect your tools with a household cleaner, such as Lysol, to avoid spreading the disease.
Once Fusarium dieback has infected a tree, the wounds and weakened condition of the tree make it susceptible to many other fungal infections and other diseases.
Originally found in Israel, Fusarium dieback was first seen in Southern California in 2003. The carrier was believed to be the tea shot hole borer, a common pest of tea plants in Sri Lanka. DNA testing, however, showed that this was an entirely new species, now named the polyphagous shot hole borer. By 2010, this borer, and the disease it carries, had become a serious threat to SoCal’s box elder trees, palm trees, black locust, and our beloved avocado trees. In 2015, a second variety of carrier, the Kuroshio shot hole borer, joined the party and started infecting the popular California palms (Washingtonia filifera). It is estimated that this disease now threatens 25% of all the trees lining Southern California’s streets.
To the naked eye, the two species of borer responsible for Fusarium dieback look identical. Female beetles are tiny and black, only 0.07 to 0.1 inches long. Males are brown and even smaller, at only 0.06 inches long. Female beetles can fly and will leave their birthplace to find other host trees to use as nurseries, carrying the disease with them when they go. Males do not fly and generally stay in the tree of their birth. These beetles are most active during summer and fall.
Fusarium dieback hosts
Shot hole borers can be found feeding on and breeding in over 200 species of woody plants. That’s a lot of potential hosts. To date, the disease has been found in more than 130 different host species.
While this disease prefers palms and ornamentals, such as maple, birch, and tulip trees, it is becoming a serious threat to avocados and California live oaks. California bay laurel, carob, chestnut, elderberries, figs, olive, peaches, persimmons, pineapple guava, pistachios, and pomegranate are also vulnerable to Fusarium dieback.
How infection occurs
This disease starts when female beetles bore into tree trunks and branches, creating galleries of tunnels. Within the tunnels, chambers are built for eggs. Female beetles have developed a symbiotic relationship with three different fungi, which they carry around in their mouths, much the way we carry around bacteria in our gut. [The fungal pathogens of Fusarium dieback are Fusarium euwallacea, Graphium euwallaceae and Paracremonium pembeum, if you enjoy the Latin.]
The fungi that set up housekeeping within the tree end up being food for the newly hatched beetle larvae. By eating the fungi, the larvae then become carriers of the disease. These fungal colonies develop very rapidly, once they are inside a tree, and there is no known treatment at this time. Complicating matters even more, not all infected trees will show signs of infection. Some infected trees simply serve as breeding grounds, without showing any signs of disease, and we don’t yet know why.
Healthy trees are far better able to protect themselves against borers. This means selecting plants appropriate to your microclimate, irrigating and fertilizing them properly, and providing healthy soil. Also, monitor your trees regularly.
Currently, Fusarium dieback is limited to Israel and Southern California. You can see a map of the disease, as it spreads through California, here. [It’s a big file, so it make take some time loading.] While Fusarium dieback has only come as far north as San Luis Obispo, to date, that can change overnight. Research is underway, to try and identify an effective lure that can be used to trap the borers.
If you suspect Fusarium dieback on a tree, please contact your local County Extension Office. Together, we may be able to slow or stop the spread of this disease.
Jerusalem artichokes are a species of sunflower with an edible tuber.
Jerusalem artichoke description
Jerusalem artichokes look like their cousins, the sunflowers, reaching 6 to 15 feet in height, with somewhat smaller, bright yellow flowers. The tubers look a lot like turmeric and ginger. Long and bumpy, these tubers can range in color from brown to white, or purple to red, depending on the species and growing conditions.
Growing Jerusalem artichokes
To grow your own Jerusalem artichoke crop, begin by selecting a site. Remember, these plants are going to be around for a long time, and they can become rather tall. Unlike many other plants, sunchokes seem to enjoy being clumped together, but they should still be planted 8 to 12 inches apart. Create soil mounds over the plantings, 2 to 3 inches deep, and water regularly, allowing the soil to dry out between waterings.
Starting with a single Jerusalem artichoke tuber, you will eventually find your garden overrun with these perennials. Each plant can produce 75 to 200 tubers every year. Left unharvested, each of those will produce tubers of their own. In my book, that’s a good thing - but you may feel differently. Since tubers left in the ground for too long tend to deteriorate, and they can become invasive, Jerusalem artichokes are a good candidate for large containers or raised beds. This will facilitate crop rotation and control the number of Jerusalem artichoke plants you end up with each year. Any little piece of tuber left in the ground is likely to sprout, to plant accordingly.
Grown in containers, Jerusalem artichokes do not need to be fertilized if you start with nutrient rich potting soil mixed with aged compost. Plants will need to be watered deeply, once a week, throughout the summer. Staking may be needed to keep plants from toppling over, or you can grow them along a fence or against a building.
Harvesting Jerusalem artichokes
As the leaves, flowers, and stems begin to die back at the end of the growing season, usually around October, you can dig up the tubers and allow them to dry, unwashed, for storage. Each plant will produce approximately five pounds of tubers. Sunchoke stems can be chopped and used for mulch, while the tubers to be used for the next year’s crop are simply placed back in the growing bed, along with some aged compost, and the cycle begins again.
[Mostly] edible sunchokes
Surprisingly low in starch, Jerusalem artichokes contain a type of carbohydrate sugar, called inulin, which gives them an underlying sweet taste. While the human gut cannot digest inulin, bacteria further down can, so some people may experience a certain ‘airiness’ after eating sunchokes. If they are not bothersome to you, they also provide a lot of potassium, iron, fiber, and B vitamins.
Or, if you prefer, you can ferment your Jerusalem artichoke crop to make brandy, the way they do in Germany.
As an older native plant, sunchokes have very few pests or diseases to worry about. So, mark your calendar to start Jerusalem artichokes in March or April, and start preparing the planting space today!
How can digging both cause and correct hardpan?
Before we can answer that question, we need to know what hardpan is.
Hardpan is a layer of soil so dense that air, water, and roots can barely move through it, if at all. Think of it as a saucer under the teacup of life. Unlike compacted soil, which is a general condition of not enough macropores and micropores, hardpan is a distinct layer, usually found 4 to 40 inches below the surface, that reduces or halts drainage, roots, and gas exchanges altogether.
Causes of hardpan
Plowing, digging, or rototilling to the same depth every year can compact the underlying soil so much that it becomes hardpan. In addition to digging and plowing, there are several other things that can cause hardpan to develop:
Hardpan can also occur naturally when layers of silica, iron oxides, salt, or calcium carbonate fuse and bind soil particles together. Glaciers can cause hardpan, by compressing layers of those minerals. Soil pH and soil structure are major factors in the development of hardpan.
Acidic soils are far more likely to cause calcium and iron to form hardpan layers, than alkaline soil. Soil structure is another important factor. Clay particles are very small and already tend to become compacted. In clay soil, rain or irrigation followed by high temperatures can also create hardpan. However it occurs, plant roots don’t like it.
Do you have hardpan?
Poor drainage is the first sign of hardpan, followed by a general failure to thrive. If you have a soil tester, you can take a few 2 or 3 foot deep samples of your soil, to see if there is a hardened layer. If you have a post hole digger, you can basically do the same thing, with more soil and more effort. The important thing is to look at the layers of soil as you bring them up. If you reach a layer where all the plant roots start growing horizontally, you have hit hardpan.
Once a layer of hardpan has formed, it takes brute strength and proper soil amendments to correct the problem. Basically, you can either dig down into the hardpan layer, breaking it up, or add significant amounts of organic matter and let nature takes its course.
If you opt for the brute strength method, you will have to wait for the soil to be dry. [Digging wet soil is never a good idea.] You can use a digging fork, spade, or broadfork to break through the hardpan layer. As you do this, you will want to make sure that the subsoil is not brought up and mixed with the topsoil.
To prevent compounding the problem by even more digging, it is important to add significant amounts of organic matter, in the form of aged compost or manure, or peat, to improve the soil structure, as you dig. Earthworms and other soil dwelling creatures will, over time, break through a thin layer of hardpan, but only if enough organic material is added to the soil.
Treating acidic soil with lime can help break up the chemical bonds that hold a hardpan layer in place. This is not an option in regions with alkaline soil. You can also top dress an area repeatedly with organic matter to treat hardpan, but it may take years before you see results.
People started growing and eating soybeans three thousand years before the invention of written language. Originally from East Asia, this high protein legume is now found practically everywhere. Soy milk, tofu, and soy sauce are just a few products made from soybeans, but what about the plants themselves? Is there a place for soybeans in your summer garden?
The soybean plant
Mature soybean plants can reach 2 to 4 feet tall, and they have trifoliate leaves. This means that each leaf is made up of three leaflets. Like other legumes, soybean roots have a symbiotic relationship with certain soil bacteria (Rhizobium) that help them use atmospheric nitrogen. They are deep rooted plants, going down 3 to 5 feet. Soybeans are photoperiodic plants. This means shortening days is what triggers them to start producing flowers. Soybean plants have small, self-fertile flowers that can be purple, pink, or white. Once flower production begins, many soybean plants drop their leaves.
Soybean fruits are 3 inch long, hairy pods that contain 2-4 seeds, called pulses. Soybean pulses can be brown, black, green, yellow, or multicolored. By 2010, 93% of soybeans grown commercially in the U.S. were genetically modified. In that same year, scientists mapped the soybean genome, the first bean to be sequenced.
Types of soybeans
There are two basic categories of soybeans: vegetable and field. Field soybeans are grown for oil production. Vegetable varieties are higher in protein, easier to cook, and taste better than field soybeans. Soybeans contain 38-45% protein and up to 19% oil.
How to grow soybeans
Soybeans (Glycine max) are an annual bean plant that loves hot, summer weather. Pulses should be planted 1 inch deep and spaced with mature sizes in mind. To provide an ongoing harvest, you may want to use succession planting, adding new plants every week or two during the growing season. Soybeans are ready to harvest within 80-120 days after planting. Pick pods while they are still green. Once they brown, the pulses lose flavor. Of course, you can always use mature pulses to plant the next season's crop! Because of their nitrogen-fixing ability, soybeans make an excellent player in crop rotation plans.
Soybean pests and diseases
Spider mites are the most destructive pest of soybeans, followed by corn earworm moths, Mexican bean beetles, bean leaf beetles, and cyst nematodes. Fungal diseases, such as stem blight, rust, and white mold can infect soybean plants, along with bean yellow mosaic and other viral diseases. But don't let that stop you!
If you have the space, give soybeans a try in your yard!
Wrapping your trees to protect against winter cold sounds like a good idea, but it probably isn’t.
For decades (centuries?) people have wrapped their trees to protect against frost cracks, winter sunscald, and other forms of cold weather damage. While this sounds like a great idea, it ends up that those wraps can actually cause more harm than good.
The theory behind tree wraps
Winter tree and plant damage can occur in several ways: flat out freezing; temporary warming, followed by freezing; and cracks caused by the water within the plant freezing, expanding, and pushing its way out. When you get down to it, it is rapidly fluctuating temperatures that cause the most damage to trees in winter.
Types of tree wraps
Tree wraps, also known as tree guards, or tree liners, can take many forms. Commercially available tree wraps include white plastic guards, white adhesive tape, foil-backed fiberglass panels, capillary mats, landscape fabric, reflective greenhouse insulation, and watering bags. DIY growers have used paper, bubble wrap, burlap, cardboard, shredded newspaper, foam, and I have a neighbor who knitted sleeves for her trees!
It's very colorful, and I like to think that the good airflow allows moisture to evaporate enough to keep the trees healthy.
Some people make their own tree wraps by creating a tube of chicken wire fencing around the trunk and filling the space in-between with shredded leaves. All of these methods require frequent inspections to avoid becoming problematic.
Problems with tree wraps
According to the International Society of Arboriculture (ISA), studies have shown that tree wraps do not actually prevent temperature fluctuations. In some cases, temperature variations are even worse with the wraps. Also, tree wraps provide protection for many wood-boring insects, wasps, and earwigs, just to name a few. This is especially true with snugly fitting wraps.
Manufacturers and many gardening sites suggest that tree tubes be left on young trees for several years, until they are well established. They claim that tree tubes insulate the trunk against winter sunscald and shade it against summer sunburn. These tubes may also prevent a tree from swaying in the breeze so much that it fails to get strong, through a process called thigmomorphogenesis. [How’s that for a cool garden word?]
Wrapped too tightly, tree wraps can interfere with normal growth, causing girdling. Depending on the material used, it may cut into the bark, causing points of entry for pests and disease.
Often bare root stock and young trees are sold with tree wraps in place. These wraps can provide protection during digging and shipping, but they can also hide injuries, insects, and improper pruning.
Wrapping your trees may reduce mechanical damage and rodent feeding, but it is more likely to result in insect damage and fungal disease. And it will not protect your trees against frost cracks or winter sunscald. Personally, I prefer whitewashing, mulch, and proper irrigation to prevent cold weather damage.
Summer sunburns hurt, but winter sunscalds are worse (for trees).
You might not think sunscald, or sunburn, could occur in winter, but it can. [Ask any of your skier friends. They know.] Unlike summer sunburns, which are much like the sunburns we get, winter sunscald occurs when it gets warm enough in the daytime for plant cells just under the bark to break dormancy.
There are several chemical changes that occur as plants enter dormancy. These changes protect plants against the cold. Warm, sunny days can trick overeager cells into breaking dormancy and losing those protections. Then they die, leaving a sunken area below the bark.
If there are any fruits present in winter, they, too, can be affected by winter sunscald. This occurs when fruits that were protected by shade are exposed to direct sunlight. The outer skin of these fruits can become damaged enough to allow insects and disease to enter. In other cases, the fruit may look normal on the outside, but the underlying tissue becomes damaged and is usually inedible.
Winter sunscald is rarely fatal, except to one- or two-year old trees. However, it can weaken a tree and make it susceptible to wood-boring pests and canker diseases. Nearly all fruit trees and all newly planted trees are vulnerable to winter sunscald. Thin barked trees, such as ash, beech, birch, honey locust, linden, maple, oak, white pine, and willow tend to develop winter scald, if left unprotected.
Preventing winter sunscald
There are several ways you can prevent winter sunscald from damaging your trees. First, keep your trees properly irrigated. A water stressed tree is far more likely to develop winter sunscald. Also, avoid damaging the trunk with lawnmowers, car doors, and weedwackers. Damaged trunks have a harder time protecting themselves. You can prevent mechanical injury and stabilize soil temperatures with a thick layer of mulch around the tree. Just be sure to keep the mulch from touching the trunk, which would set the stage for fungal disease.
If watering and mulching aren’t enough, whitewashing the trunk and exposed surfaces of major branches can help prevent winter sunscald. It will protect against summer sunburn, too. Some people find the paint unattractive. Personally, I like it. Just don’t whitewash your trees with enamel paint. They will suffocate. Instead, combine 1 part water with 1 part white latex paint (preferably one without extra chemical additives) and use that to paint your trees.
Traditionally, tree wrapping was recommended as a protection against winter sunscald, but we now know that those wraps can cause more harm than they prevent. Wraps allow moisture to collect, setting the stage for rot, and they provide an excellent hiding place for pests and fungal disease. Also, cracks that occur under the wraps tend to not heal as well. Bottom line: don’t wrap your trees.
If your trees tend to get winter sunscald, you can block or shade the southwest side of your trees to provide some protection against winter sunscald.
Winter sunscald care
Once damage has occurred, you can speed the healing process by smoothing the edge of the wound with a sharp, sterilized knife. Do not remove more than 1/2” of the bark. Also, resist the urge to paint tar or sealant over the wound. This usually traps moisture against the wound, increasing the chance of disease and decay.
Finally, you know that old adage about getting lost in the woods and looking for moss on the north side of trees? Well, that piece of advice is useless. Moss grows on the side of the tree with the most moisture and sun protection. What you can do, however, is look for winter sunscald, which nearly always occurs on the south or southwest sides of trees in the northern hemisphere.
Now you know.
You can grow a surprising amount of food in your own yard. Ask me how!
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