Bark is far more than just a protective coating. Let’s learn some of the basics about bark.
First, we will take a cross-sectional look at a tree trunk, from the inside out:
How bark is born
Young stems of woody plants do not have bark. Instead, from the outside in, they have an epidermis (skin), cork (periderm), cortex, primary and secondary phloem, vascular cambium, primary and secondary xylem, early wood and late wood (each double ring represents one year of growth), combined with the primary and secondary xylem, and the pith. As the stem grows, the cork gets thicker, pushing the skin away from the wood. Isolated from water- and nutrient-carrying vascular tissues, these cells die and become what we recognize as bark. This tough, outer surface helps keep water in, and pests and diseases out. It also provides protection against temperature extremes and sunburn damage. [The skin of a potato, being a modified stem, is actually the cork.]
What is bark?
Bark is mostly lignin. Lignin is the material that makes trees stand up. Bark also contains tannins. Tannins are believed to inhibit decomposition. Bark is made up of two distinct parts, the living phloem and the dead periderm. Phloem is the vascular tissue responsible for helping sap flow downward throughout the plant. The periderm is made up of cork (phellem), cork cambium (phellogen), phelloderm, and the cortex. Within the periderm are large spaces that allow gases to move from the tree to the atmosphere and vice versa. These spaces are called lenticels. As a tree grows, and inner layers are pushed outward, the lenticels create unique markings that are used in tree identification. For example, silver birch trees (below) have distinct horizontal lines which are the lenticels.
Types of bark
Bark comes in many shapes, colors and thicknesses. Bark is generally described by its texture. It can be smooth (American beech), scaly (black cherry), plated (black birch), warty, shaggy, papery (paper birch), furrowed, or fibrous. They ridges can also be useful when identifying a tree. Bark may form vertical strips (red maple), ridges (white ash), ridges that are broken horizontally (white oak), or it may be uninterrupted ridges (red oak).
Did you know that cinnamon is actually the bark of trees?
And those little plugs that protect your wine are bark from the Quercus suber (cork oak) tree.
Braconid wasps are tiny heroes of the garden, though rarely seen.
The list of edibles protected by braconid wasps is too long to include here, but it would include grapes, peaches, nectarines, apricots, tomatoes, apples, prunes, plums, broccoli, rutabagas, turnips, and cabbage, just to name a few.
Braconid wasp identification
There are over 12,000 different named braconid wasp species, worldwide, with another 40,000 or so, yet to be identified. Most are dark brown or black with reddish accents. It is estimated that there are 1,700 different braconid wasps in North America and they are all stingless. Braconid wasps can be as small as 1/13 of an inch long, or as big as 5/8 of an inch. If you can get one to hold still while you go find a hand lens, you would be able to see that these tiny wasps have antennas with 16 or more segments! What you are more likely to see are their oblong, white or yellow eggs sticking out of a host insect.
Braconid wasp diet
Adult braconid wasps, while they eat mostly pollen and nectar, are beneficial because they parasitize many garden pests. This means that they lay their eggs on or in other insects. When the eggs hatch, the larvae eat their host. Garden pests vulnerable to parasitization by braconid wasps include:
Attracting braconid wasps to your garden
Parasitic and predatory wasps are attracted to mixed plantings that provide nectar and pollen, along with insect prey. To make your garden and landscape more appealing to these beneficial insects, be sure to include a wide variety of flowering plants at various stages of development throughout the growing season.
What’s that grey mold that appears overnight on your strawberries? Where did it come from? And how did it happen so fast? Strawberries can go from nearly perfect to practically inedible in an astoundingly short time. Read on to find out why!
Botrytis cinerea is everywhere. It flies in on the wind, it is carried on clothing, shoes, tools, pets; it’s floating around in the air we breath. Yep, it’s like that. So, unless you live in a bubble, your plants and food are already in contact with grey mold. There are actually several different strains of grey mold. They get their Latin name, Botrytis, from the Greek words for ‘grapes like ashes’. You might think that’s because they feed on grapes, but it is actually because the fungi itself grows in clusters. The word ‘ash’ refers to the grey color.
This particular garden problem spends most of its time as a dormant, asexual spore that is relatively indestructible. Add moisture in spring (or with irrigation) and voilà, stuff starts to happen!
Grey mold - This is the gray fuzz we find on our strawberries, grapes, and other fruit and flowers.
Noble rot - If dry conditions follow wet weather, the fungi suck moisture out of grapes, leaving behind a bitter aftertaste.
Antifungal - If that weren’t bad enough, botrytis also interferes with wine-making! As it grows, it produces an antifungal substance (presumably to kill off the competition) that also kills off the yeast that makes grape juice magically transform into your favorite Chardonnay or Pinot Noir.
Bunch rot - As soon as an injury occurs to grape vines or fruit, the botrytis fungi cause bunch rot infection.
Most commercial grape growers apply fungicides to prevent infection, since the fungi is present all the time. As wth downy mildews, black spot, and powdery mildew, moisture control is the key. If leaves and fruit are left wet, they are more likely to become infected. [Remember those strawberries you washed before putting them in the fridge last night? Yep, that’s what happened!]
Controlling grey mold
Once infection begins, potassium bicarbonate-based fungicides can be applied to reduce the spread of the disease. Dead and diseased plant tissue should be carefully removed. I say ‘carefully’ because each bit can contain millions of fungal spores.
Some people have an allergic reaction to grey mold that causes a rare lung disease known as ‘winegrower’s lung’.
So, the next time you buy strawberries or grapes, wait until you are ready to eat them before rinsing them off. It’s not a guarantee, but it helps! Also, keep them in their container and put them in the crisper drawer. Strawberries are best stored at 32 to 36 degrees F, at 90 to 95% humidity.
Black spots on leaves and petals is a sign of disease.
Spring and summer fogs and dew can leave behind just enough moisture to create breeding grounds for several different bacteria and fungi. While there is a specific disease called black spot, there are other bacterial and fungal diseases that can cause black spots, including citrus blast, common leaf spot, bacterial spot, anthracnose, bacterial speck, and entosporium leaf spot. Black spot mostly attacks roses, but its presence can indicate potential other problems in the garden or landscape.
What are the black spots on my leaves?
Black spots on leaves, fruit, canes, stems, and twigs are areas where a pathogen is breeding and feeding on plant tissue. These black spots are generally round because the infection begins at one point and spreads out equally in all directions. The spots have perforated edges and can reach one-half inch in diameter. As the area of dead tissue expands even larger, it can take on many different shapes. There may be a yellow halo around these leaf spots and yellowing in the surrounding plant tissue.
Black spot: the disease
The black spot disease is caused by a fungus called Diplocarpon rosae. These fungi spread through rain and sprinkler splash, and wind, to tender new growth. This disease usually spreads from lower leaves, moving upward. Tools used on an infected plant can also spread the disease to other plants, so be sure to sterilize tools with a 1 part bleach, 9 parts water solution, or spray tools with bathroom cleaner after each cut when working with a potentially infected plant.
Black spot treatment
Once a leaf is infected, there isn’t anything you can do for it except remove it from the plant and throw it in the trash. Antifungal sprays, such as Bordeaux mixture, can be used to prevent future infection and at the first sign of the disease. Sulfur or diluted neem oil can also be used. Treatments will need to be repeated every 7 to 10 days for as long as temperatures are between 75 to 90 °F.
Preventing back spots
As usual, prevention is a lot easier (and more effective) than treatment. These tips can go a long way toward preventing the problem of black spot in the first place:
Shade tree decline, or shade tree disorder, is a term used to describe branch and twig dieback in the crown of a tree. These trees are not being affected by pests or disease, per se, but they are very unhappy trees.
Before we begin, go outside and take a quick look at the trees. Go ahead. I’ll wait.
Okay, so, what did you see? Of course, it depends on the season. In winter, most deciduous trees will be bare naked. By late spring and early summer, healthy trees should be covered with leaves, a thick blanket of sugar producing machinery! Every leaf surface should be cranking out energy as fast as it can. What you probably saw, especially if you are in California, is sort of healthy-looking trees that were a bit thin on top. This is not a hormonal problem that can be treated with hair tonic. This is serious business and those trees are dying.
Drought (or lack of proper irrigation) is the number one cause of shade tree decline, but there are other causes, and it is not only seen in ornamentals. Canada’s sugar maple trees have been exhibiting shade tree decline for decades. In that case, the decline is due to air pollution blowing northward along our Eastern seaboard. [My sincere apologies, Canada.] There are many other causes (and few solutions) to the problem of shade tree decline.
Symptoms of shade tree decline
Symptoms of shade tree decline appear gradually and, like the frog in the pot, we often don’t even notice until severe damage is done. Initial signs of shade tree decline include:
Later symptoms include:
These are all signs that the tree knows it is dying and is trying to put what little energy it has remaining into the next generation. Most trees affected by shade tree decline die within a few years.
What causes shade tree decline?
Imagine getting pummeled all day, every day. Professional boxers do it, but they have strict nutritional support, medical teams, and proper hydration. Our trees have been getting pummeled by drought, pollution, and injury for many years. In addition to drought and pollution, the following injuries can contribute to shade tree decline:
The down side of shade tree decline
Trees are a big investment, financially, and they take time to grow. They also prevent erosion, provide shade (and food), store carbon, create the oxygen we breath and filter pollutants out of the air. They provide habitat and food for many other living things, promoting biodiversity. As a tree begins to suffer shade tree decline, it becomes less able to defend itself against pests and diseases, and it is more likely to suffer sunburn damage, providing easy entry to borers and other insect pests.
The bigger problem
The Carnegie Institute for Science reports that California has lost an estimated 66 million trees in the last five years. Even if heavy rains appear, they say that won’t be enough to prevent the future loss of “tens of millions of trees” in California alone. They are using a type of spectrometer that analyzes the molecular composition of trees as they fly overhead. This amazing equipment can tell when a tree has lost too much water to recover. These dead and dying trees now harbor pests and diseases in epidemic proportions. This large-scale die off also makes it easier for invasives to get established, and they pose a major fire hazard.
Preventing shade tree decline
Prevention is much easier, and more likely to succeed, than treatment. If you have trees, such as birch, willow, or Japanese maple, that evolved to live in the shaded understory, or near a creek or stream, you will have to recreate those conditions to prevent shade tree decline. You can do this by:
Treating shade tree decline
Prospects for an affected tree are not good. The damage has already been done and even the most diligent care may not be enough. If you are determined to try, these actions may save your tree, or help it to survive a little longer:
How to irrigate trees
Most trees have the majority of their roots in the top 12 to 18 inches of soil. When these roots get too dried out for too long, they die. This reduces the amount of water available to the tree for life processes and cooling (and growing new roots). While it ‘feels’ right to water a little bit every day, this actually encourages shallow root development. Deeper roots are better protected from the elements. Properly irrigating trees means getting the water to a depth of at least 5 to 7 inches every 3 or 4 days, during drought. Before we knew better, we used to plant trees in bowl-shaped depressions that would then be filled with water. Sounds good, but it’s a bad idea. This practice leads to crown rot and several other fungal diseases. Better methods include soaker hoses and tree rings. Tree rings can be mechanical devices, or they can simply be trenches dug around trees at the drip line. Fill the trench every few days during the peak of summer and your trees will thank you.
Selecting the right trees
If it is too late to save your tree, invest in a reputable arborist for professional removal. Trees can be deadly. Seriously. Then, use the following information to select trees best suited to your microclimate (and be sure to irrigate them properly):
Fighting Mother Nature is a full-time job and, honestly, it’s mostly a waste of time. Rather than setting ourselves up for tons of maintenance in a never-ending battle, put the very things that occur naturally to work for you. There are plenty of trees and shrubs that have millions of years of evolution behind them, making them a perfect choice for a specific area.
Plant those instead.
We’ve all seen those cans of yellow wax beans in grocery stores, but these plants are easy to grow, they add nitrogen to your soil, and the crisp sweetness of a freshly picked bean far surpasses anything canned.
Wax beans (Phaseolus vulgaris) actually refers to several different yellow-podded members of the common bean family. This family also includes lima beans, kidney beans, pinto beans, and immature ‘green’ beans. It is believed that wax beans got their name because the yellow color looks similar to beeswax, but no one is really sure. Wax beans are available in both bush and pole varieties.
How wax beans grow
Beans are self-pollinating annuals. These plants are fun and rewarding to grow. They grow quickly enough to work well as a children’s activity, reaching maturity in only 60 days. What’s really fun about these plants is that they can be grown pretty much anywhere: on a windowsill, in a container, in a straw bale, and in partial shade. Of course, they prefer sunny raised beds or traditional garden rows, but, the point is, these plants are EASY. Like other legumes, wax beans are able to ‘fix’ atmospheric nitrogen, making it available not only to themselves, but to nearby plants. Of course, this only works until the plant starts producing seeds, then the free lunch is over.
How to grow wax beans
Like other beans, wax bean seeds are mostly endosperm (plant food). Plant seeds one inch deep and 2 to 4 inches apart. If you grow bush beans (not the canned barbecue product), your plants will get 18 to 24 inches tall and about a foot wide, so thin accordingly. Pole beans, however, can be trained up trellising, fences, lattice, sunflowers, trees, pretty much anything they can wrap their tendrils around, without thinning. They can also be used in the traditional Three Sisters Method, with corn and squash. Trellising pole beans on something that goes over your head looks really nice, with ripe beans hanging down, from overhead. It’s makes picking easy, too! Some people say that planting marigolds nearby can be a problem, claiming that they interrupt the nitrogen-fixing capabilities of legumes, such as peas and beans, but I don’t know if this is true.
Wax bean pests and diseases
When it comes to bean pests, it’s all the usual culprits: cutworms, bagrada bugs, cucumber beetles, weevils, thrips, wireworms, leaf miners, and dried fruit beetles. As delicious as fresh wax beans are, it’s no wonder so many critters are after your harvest. Bindweed can also choke out your bean plants. Common wax bean diseases include anthracnose, bean mosaic, and fusarium wilt. Wax beans should not be planted near soybeans to reduce the likelihood of stem blight.
Angular leafspot is a bacterial disease that affects strawberries, cucumbers, melons, squash, and spinach.
There are several different angular leafspot (ALS) diseases in California, depending on the host plant and the pathogen that causes it:
There is also an ALS variety that attacks common and snap beans, but it has not been seen in California, as far as I know. The disease can also affect cotton, but I don’t figure any of you are growing cotton - though it might be interesting…
Angular leafspot symptoms
At first, the disease appears as tiny lesions on the underside of leaves (A). As the disease progresses, pale, angular spots appear on the upper surface (B) and grow larger. [These areas are not angular because the bacteria are OCD. Instead, it is because they tend to occur between leaf veins, which dictate the angles.] Eventually, infected areas turn reddish-brown (C), with a yellow or black halo. In cucurbits, the infected areas look more gray or tan than brown, and in spinach the infected areas are very dark. Lesions often appear next to leaf veins and in the calyx (the structure that surrounds and protects flower buds). The bacteria produce an ooze that looks like mucus in the morning and dries to a scaly, white sheen, as the day progresses. This is probably the easiest way to diagnose angular leafspot. Extreme infections can be mistaken for crown rot.
How angular leafspot is spread
The bacteria that cause angular leafspot overwinter on plant material and in the soil, waiting for one thing, and one thing only: moving water. A raindrop, a sprinkler spray, a squirt from the hose can send millions of bacteria in every direction. They can also catch a ride on garden tools, your shoes, your friends’ shoes, and your pet’s feet. Seeds can also be infected.
Controlling angular leafspot
Using only resistant, certified disease-free plants and seeds is the easiest way to avoid infection. This is one of many arguments against starting plants from grocery store purchases. As tempting as it may be, these plants can harbor many plant pathogens that, once introduced, are difficult to eliminate. Chemicals have not been shown to be effective against angular leaf spot. Crop rotation can reduce the likelihood of this disease getting a foothold in your garden or landscape. You can also help reduce infection by only harvesting when plants are dry. Copper has been shown helpful if it is applied just prior to cool, rainy weather.
Finally, for the sake of your plants' health, avoid overhead watering.
Cucumber beetles are major pests of cucumbers, melons, squash, and other cucurbits.
There are three major classes of cucumber beetle in California: spotted, striped, and banded. Banded cucumber beetles are mostly found in southern regions, while striped and spotted cucumber beetles begin emerging in late spring and can have as many as three generations in a single season in the Bay Area.
Cucumber beetle identification
Cucumber beetles are relatively easy to identify. They are small, only one-quarter of an inch long, and they have shiny black heads. The larvae are yellowish with a dark head. Other identifying marks, by species, include:
Cucumber beetle damage
Adult beetles overwinter in the soil and lay their bright orange eggs at the base of host plants. When these eggs hatch, ravenous larvae start feeding on plant roots. Adults will feed on roots, blossoms, leaves, and plant crowns, along with fruit, as they feed. This is especially true for tender, new growth. Cucumber beetles can easily kill seedlings, and they feed on far more than just your cucumbers. Other favorite plants are corn, beans, lentils, roses, and grasses, along with your melon and squash plants. They are also attracted to ripening stone fruit. Holes in leaves may be the first obvious sign of infestation. Cucumber beetles can also carry squash mosaic virus (for up to 20 days after feeding on infected fruit), and bacterial wilt, a fatal cucurbit disease.
Controlling cucumber beetles
Cucumber beetles are difficult to control. Parasitic tachinid wasps provide some assistance, so avoid broad spectrum pesticides, which will kill off your helpers along with the pests. Cucumber beetles prefer cool, moist places, such as under your squash or melon plants after they have been watered. That makes it the best time to look for these pests and squish them as soon as you see them. They can bite, so wearing gloves is a good idea. Since cucumber beetles can fly, battling them is an ongoing process. Regular monitoring is your best defense.
Overspray, also known as drift or carryover, occurs when someone else’s herbicide reaches your plants. It rarely ends well, and it can make for strained relations.
And sometimes you do it to yourself! Those pesky weeds coming up through the patio blocks or on pathways are such a pain to dig out. One quick spray and you're done, right? Wrong. But, there is a slightly easier way, so read on!
Very often, overspray is accidental. A quick breeze appears, temperatures shift, or a happy canine comes on scene. In other cases, overspray is the result of thoughtlessness, ignorance, or even vandalism. From your point of view, it makes no sense. One day, your plants are thriving. The next day, something is definitely wrong.
Symptoms of herbicide damage
The symptoms of herbicide damage vary, depending on the type of chemical being used. Broadleaf weed killers cause leaves to twist and cup, and new leaves are narrower than normal. Also, the roots of annuals will come to the surface. These herbicides will, as advertised, cause grasses to yellow and die. Non-selective herbicide overspray will cause chlorosis, poor health, and dieback, if not rapid death. Other symptoms of herbicide overspray include leaves turning purple, stem dieback, and leaf mottling and spotting. These symptoms can indicate other problems, too, so it can be difficult to diagnose overspray.
How overspray occurs
Sometimes the best indicator of a problem is having seen your neighbor applying chemicals the day before. Many herbicides are applied as a spray. This means that vapor can spread to areas where it is not wanted, especially if there is a breeze, low humidity, or high temperatures. According to UCANR, herbicides can travel for miles on the wind. And those convenient handheld spray bottles look safe, don’t they? But, when you squeeze that handle, it is all too easy for the spray to bounce off your intended target, the soil, or your shoe, and land someplace else. That contaminated shoe can now carry the herbicide to new plants. After the intended application is complete, the soil around treated plants also contains herbicides. This soil can be kicked, carried on the sole of a shoe, in gardening tools, or on a breeze to places where herbicides are not wanted.
There are several ways you can prevent overspray from damaging or killing plants you never meant to harm:
Treating victims of overspray
Large perennials can often be saved from the effects of overspray, if it is caught soon enough, because the chemicals move more slowly through the vascular tissue of these larger plants. Leaves that have come in contact with an herbicide should be removed, to halt the spread of the chemical. Plants should be hosed off and watered well. Of course, the water that comes off the plant will contain herbicides, which can then spread to new locations. [Oh, what a tangled web we weave…] Anyway, watering the plant thoroughly will help to dilute the chemicals. These plants will require special care for at least a year. Left untreated, they will eventually die. Tender annuals and edibles should be removed from the garden and disposed of in the trash (not the compost pile). Even though you might be able to keep these plants alive, do you really want those herbicides in your food?
Finally, keep in mind that you can be held legally liable for damage caused by overspray, even if it was unintentional.
As for those pesky sidewalk weeds, grab a sharp knife or screw driver and cut them off at ground level. Then, pour a liberal amount of vinegar over the area. It may not kill the root completely, but it will take the plant a lot longer to come back, if it does at all.
Tomatillo plants are free spirits and they make delicious salsa verde!
Unlike most other agricultural plants, tomatillo plants refuse to be hybridized. This is pretty surprising, since recent research has shown that tomatillos have been around for 52 million years! They have retained their wild nature while still providing us with an easy to grow edible plant. These members of the nightshade family (Solanaceae), are cousin to tomatoes, potatoes, peppers, eggplant, and tobacco. As such, you should not eat any part of the plant other than the fruit.
Tomatillo fruits are greenish and sticky. They come wrapped in their own natural paper husks. The plants, being wild by nature, can take on a variety of shapes and sizes, but they tend to be low-growing, sprawling plants. If you want something really unique, you can even find purple tomatillos! Tomatillos are one type of ground cherry, but there are many others.
How to grow tomatillos
Native to Mexico, tomatillos (Physalis philadelphica), also known as Mexican husk tomatoes, prefer bright, sunny locations and they are somewhat drought tolerant. They grow best in nutrient rich soil with a neutral pH. Adding compost to the bed before planting will help give your tomatillos a head start. The plants grow quickly, but they take a long time to produce fruit (60 to 80 days). Tomatillos are not self-fertilizing, so you will need multiple plants to get a crop. Seeds should be planted 1/8 to 1/4 inch deep. Tomatillos can be grown in large containers (at least 5 gallons) but they need more sunlight than a window garden can provide. Like peppers, tomatillo seeds need warm temperatures to germinate.
If you buy tomatillo seedlings, plant two-thirds of the stem below ground, as you would for tomatoes. All those stems will covert to root tissue, helping your new plants get a better start and produce a bigger harvest. Place mature plants three feet apart and provide support with trellising or tomato cages. Like tomatoes, you will want to keep the soil around your tomatillos moist, but not soggy. Mulching can reduce evaporation and competition from weeds. It also stabilizes soil temperatures.
Tomatillo pests and diseases
Being relatively wild, tomatillos are pretty rugged. Fungal diseases, such as powdery mildew, can occur if plants are left to sprawl on the ground, which is why providing support is a good idea. Flea beetles may also chew holes in the fruit.
Harvesting and storing tomatillos
Tomatillos stay greenish, so color will not tell you when it is time to harvest your tomatillo crop. Instead, watch to see when the fruit has filled its husk to bursting. If the fruit is left to ripen further, it will turn yellow or purple, but it won’t taste as good. Once your tomatillos are picked, you can store them in a paper bag in the refrigerator for 2 or 3 weeks, or you can make your own salsa verde and do some canning!
Love me tendril
Be my feet
Never let me go....
[Sorry, I couldn't resist.]
If you are growing squash, cucumber, peas, pole beans, or grapes, you have seen tendrils.
Tendrils are modified stems, leaves, or petioles, depending on the plant. In case you don’t know, petioles are those tiny stems that connect leaves to twigs. Rhubarb is a petiole, but I digress.
Tendrils are used to help a plant climb or hang onto supports. Tendrils can even photosynthesize, but the really amazing thing about tendrils is that they can use chemicals in the air to help them decide which way to turn!
The evil side of tendrils
Not all garden plants mean well by their neighbors. In fact, it’s pretty much a battle zone out there. The delicate, innocuous-looking tendril often has evil motives, using its tight curling abilities to choke the life out of the competition, or even to invade and parasitize other plants.
No, this is not what you think. Tendril perversion is a geometric phenomenon that occurs when a tendril switches the direction of the curl (chirality) halfway to its destination. It ends up being very common, but no one is really sure why it happens.
If you are very, very patient, you can get a tendril to wrap around whatever you like. The biggest mistake people make when attempting this is to confuse the plant by providing multiple points of contact via fingers and the intended support. If you handle tendrils delicately, you can wrap them around a wire or other support multiple times, making sure that the end is tucked under, holding it in place. You can also use other supports, such as narrow bamboo poles, to hold the lower stem in a position that keeps the tendril where you want it, until it grabs on for itself.
Tendrils are lovely to look at, but they are only so strong. If you are growing pumpkins or melons up a trellis, you may need to provide hammocks for the fruit as it grows.
Unless you’re using a syringe filled with syrup, you’ve never really fed or watered your plants.
When you irrigate or fertilize your plants, what you are really doing is watering and feeding the soil. It is the soil that feeds and waters your garden and landscape plants. Creating healthy soil is the best way to grow healthy plants that need less protection from pests and diseases, produce more flowers and food, and require less work. So why is improving soil health one of the last things on our garden To-Do lists? Let’s learn more about growing great soil.
What is great soil?
Soil is a highly complex natural body that scientists call the pedosphere. Some call it the Earth’s living skin. Soil stores water and nutrients, filters our drinking water, helps break down toxic wastes, and is a critical player in carbon cycling, nitrogen cycling, and, let’s face it, life on Earth. Soil is made up of minerals, dead things, living things, gases, and liquids. Great soil has spaces between its bits. These spaces, called macropores and micropores, hold and allow water and gases to flow, carrying nutrients to your plants. Great soil is rich in organic matter. Organic matter is made up of living things, and things that used to be alive. Great soil also contains the 17 primary nutrients required for plant development. But before you can grow great soil, you need to know what you already have.
What is in your soil?
The 17 primary plant nutrients are called macronutrients. Plants use the inorganic form of these mineral elements (read molecule-sized rocks). The only way to really know what is in your soil is with a soil test from a reputable local lab. By local, I mean on whichever side of the Rocky Mountains you reside ~ the tests used are different for each region. The Olson test is better for the west coast, while the Brays test is better on east coast. Now, when your results arrive, you may be little confused by the information. That’s to be expected. Most of us do not read lab results on a regular basis. Here in the Bay Area, we tend to have clay soil that is highly prone to compaction. Aeration is frequently needed. Clay soil tends to contain plenty of most of the necessary minerals, and too much salt and phosphorous. Iron and nitrogen deficiencies are common in the Bay Area. Other areas and soil types have other strengths and weaknesses. Your soil test results should include percentage ratings for each of the major plant nutrients. It may also tell you how much organic matter is in your soil.
Organic matter in soil
Organic matter is critical to soil health, and it can range from 1 - 8%. As living things die and begin to breakdown, they add nutrients and improve soil structure. They also alter the electrical charge of soil. Quick chemistry review: molecules can be stable, with no charge, positively charged cations (cat-ions), or negatively charged anions (an-ions). Calcium, potassium, and many other plant nutrients are cations, while organic matter tends to be anions. Plants need both. Ensuring that there is enough organic matter in the soil also improves porosity, aeration, and biological activity.
Soil is usually described as being sand, loam (silt), or clay. Sand is big. You can see individual particles. And water and nutrients can drain away quickly. Loam is made up of medium-sized particles that hold a good balance of gases, liquids, minerals and organic matter. Clay is made up of extremely tiny particles that can hold a lot of water and minerals. [It can also turn into concrete, especially if you add sand.] Organic particles surrounded by clay are protected from the microorganisms that break them down into nutrients that can be used by plants, creating an unattainable banquet. Identify your soil structure with the test found here. Each type of soil benefits from the following:
Do you see a theme here?
Adding organic matter to soil is critical to plant health. A 1% increase in organic matter can make a profound difference in soil structure (aggregation) and chemistry. This helps plant roots get to and absorb nutrients. You can add organic matter to your soil by:
Once you’ve increased the amount of organic matter in your soil, you will want to add nitrogen. Nitrogen levels are the single most limiting factor in most gardens, and organic matter can help your plants access the nitrogen that is already present. Nitrogen is a highly mobile nutrient and it is easily lost. Most soils contain less than 1% nitrogen, while 2-5% is ideal. But it is not simply a matter of adding more nitrogen. Which form will you use? Inorganic nitrogen can be found as nitrites or ammonium. When roots take up nitrates, they increase the pH of the immediate area, making it more alkaline. The opposite is true when plants take up ammonium, making the soil more acidic. Organic sources of nitrogen include blood meal and cottonseed meal, both of which will acidify soil.
You can’t know which form of nitrogen is right for your soil until you know its pH. Soil with a low pH makes it harder for plants to access some macronutrients. Soil with a high pH does the same thing. Most plants prefer a pH of 6.0 to 6.5 to thrive. Growing great soil means identifying and managing your soil’s pH.
Creating healthy soil
Soil creation is called pedogenesis. You can create great soil in your garden and landscape when you:
Other ways you can improve your soil’s health is by growing cover crops, using crop rotation, installing foot paths to reduce compaction, and avoiding irrigation run-off and urban drool.
What will you do for your soil today?
Organic gardening and farming are on the rise. But what does ‘organic’ really mean? Let’s find out.
The word ‘organic’ simply means that something is made from materials that were, at one point, alive.
The term ‘organic food’ means different things in different countries. In some countries, it means absolutely nothing. In the United States, it refers to food produced by certified organic farming methods. Certified organic farming uses the following practices:
In a perfect world, organic foods (and clothing) would be exactly that, but we don’t, so it isn’t. Car fumes, GMO pollen, reckless profiteering, and countless other inputs make purely organic farming an impossibility. It is, however, still worth aiming for.
Organic pesticides and fertilizers
Many organic farmers still spray crops with chemical pesticides and fertilizers, it’s just that the chemicals they use must be from natural sources, and they must be dispensed using equipment that was not used with synthetic chemicals. That being said, some of the ‘natural chemicals’ used in organic farming are pretty awful. Just because something occurs naturally doesn’t mean it’s safe to eat. Death cap mushrooms are a perfect example. Also, good intentions are not always enough. Horse and cow manure are excellent for composting, but are you certain about which medications, diseases, or other ingredients might come along with that manure? Good cultural practices, garden sanitation, biodiversity, and composting can all help reduce the need for any type of chemicals in your garden or landscape.
Mulch is an excellent way to protect unplanted areas, but where did it come from and what is in it? Mulch from tree trimmers is usually a good bet (and free!), but there is still no guarantee that the trees weren’t diseased or sprayed with chemicals. Even worse, mulch made from discarded lumber may contain arsenic. Yikes! You can use your own yard waste to create a relatively organic mulch and reduce landfills as the same time.
Organic potting and planting soil
Deciding to grow your own food isn’t as simple as it sounds, either. Does your bag of potting soil contain ground up car tires? What about styrofoam? Just because a bag of soil says ‘natural’ or ‘organic’ does not mean it is healthy for you or your plants. If you want truly organic, you must look for the certified OMRI (Organic Materials Review Institute) label.
Sometimes we think we’re doing the right thing and it ends up being the wrong thing. For example, if you bought birdseed from 2005 to 2008, you may have been party to poisoning the very birds you were trying to help! Scotts Miracle-Gro knowingly sold birdseed tainted with chemicals toxic to birds, fish, and other wildlife. Would using organic birdseed have been better? Probably. [Personally, I won’t be buying ANYTHING* from Scotts Miracle-Gro. EVER.]
Before despair sets in, let’s turn around and look at the positive side of things. As I said at the beginning, organic farming and organic agriculture are on the rise. Sales of organic foods and textiles are also increasing. As more certified organic farms become established, the prices of organic foods drops, making them affordable for more people. That’s all really good news. Also, for every food item that you grow for yourself, you will have a far better idea what went into that plant before you eat it.
In the world of organic gardening and farming, the bottom line is: who do you trust with your family’s health?
* Scotts Miracle-Gro sells the following product lines: Scotts, Miracle-Gro, Ortho, RoundUp, Tomcat, nature’s care. Osmocote, Substral, Evergreen, Nexa, Celaflor, KB, Fertiligene, Naturen, Weedol, Earthgro, and Hyponex, just so you know what I won’t be buying. What you do is up to you.
Wasps can transform a summer picnic into a mad scramble for safety, especially for those who are allergic. But wasps aren’t all bad.
Like bees, sawflies, and ants, wasps are in the Hymenoptera order. All these insects have, at one stage or another, four transparent wings and females often have stingers. Therein lies the problem. As a female wasp hunts down food for herself and/or her colony, she will protect herself, her family, and her food sources with extreme prejudice. In the world of insects, wasps are surprisingly intelligent.
There are over 100,000 different types of wasps (Vespidae) around the world. They tend to have long, slender bodies with a telltale wasp-waist, between the thorax and abdomen. Most wasps have two pairs of wings, though some are wingless. Wasps dangle their legs as they fly and they all have a nasty stinger. Hornets are a subspecies of wasp that are particularly aggressive. Hornets tend to have wider heads and more rounded abdomens than other wasps. Hornets can sting and bite. The variety is really pretty amazing. It’s a shame they are so painful.
Some wasps are solitary and some are social insects. Most wasp species are solitary, meaning they live alone. Social wasps live in colonies, led by a queen. Some wasps burrow in the ground, some use mud to create apartment complexes, while others build paper nests. In these nests, the queen begins laying eggs. These eggs hatch into female workers. In late summer, some eggs hatch into male drones, whose sole purpose (in their very short lives) is to mate with the queen, after which, they die. We have two major social wasps in California: yellowjackets and paper wasps. Paper wasps tend to avoid us, whenever possible. Most social wasps are predators, killing many garden pests each year. As resources become scarce and colony size grows, these wasps become scavengers. These are the ones that cause the most problems for us.
A wasp can sting multiple times and it really hurts. I used to get them caught in my long hair, as a child. There is a hornet in Japan, the Asian giant hornet, that has a stinger that is one-quarter of an inch long and it kills 30 to 40 people in Japan each year. Yikes! Did you know that only female wasps have stingers? The stinger is actually a modified egg-laying organ. Scientists say that hornet stings are more painful than wasp stings, because they contain more venom (acetylcholine). I think they all hurt and are worth avoiding. Swarms can be deadly. That being said, wasps can also be very helpful in the garden.
Wasps as beneficial insects
Adult wasps mostly eat plant matter, especially sweet nectar, sap, pollen, and rotting fruits. As they fly from flower to flower, collecting nectar and pollen, wasps also pollinate your crops. There are even wasps that have evolved specifically to pollinate figs. No wasps, no fig bars! Wasps are frequently released in agricultural fields as natural ‘biocontrols' of many common pests. The adult wasps lay their eggs on or in these pest insects. As the eggs hatch, they devour their host. (Gruesome, right? It’s brutal world out there.) Some wasps, such as the braconid, are so tiny that you’ll never see them, but they are extremely helpful in your garden and landscape. These beneficials parasitize hornworms, apple maggots, orange tortrix moths, mealybugs, aphids, orangeworms, armored scale, armyworms, artichoke plume moths, and many other pests. Some species of wasp are believed to carry certain yeasts to grapes used in winemaking!
In the case of wasp stings, an ounce of prevention is, well, you know! Use these tips to prevent getting stung in the first place:
If you are unlucky (or careless) enough to get stung by a wasp, you can reduce the discomfort with these tips:
If an allergic reaction occurs, get medical attention IMMEDIATELY.
Did you know that the golden paper wasp (Polistes fuscatus) is the only insect on Earth that has been shown to use facial recognition to identify individuals? Maybe that’s why some people get stung more than others…
Yarrow is a trouble-free plant that offers many benefits in your garden or landscape
Yarrow (Achillea millefolium) is native to all of the temperate (non-polar and non-equatorial) regions of Earth. Traditionally, the above ground portions of yarrow, also known as the nosebleed plant, old man’s pepper, soldier’s woundwort, and thousand-seal, was used medicinally to stop the flow of blood from wounds, ease toothache, treat digestive discomfort, and to induce sweating. The science behind what yarrow can and cannot do is limited. It is a mild sedative. Some studies have shown that it can relax the smooth muscle of the uterus, so it should not be taken by pregnant women. Yarrow may also be able to intensify the effects of blood-thinning and blood pressure reducing medications, lithium, and sleep aids. Also, yarrow is believed to slightly increase stomach acid. Even if you never touch the stuff, yarrow is a good addition to a landscape. It looks nice in containers, too.
The yarrow plant
Yarrow makes an excellent ground cover. If mowed regularly, it will remain prostrate. If left to its own devices, it will grow to be a foot or two tall. The lovely feathery leaves feel soft and delicate to the touch, but these plants are tough. I don’t do anything for mine and they just keep on growing. Yarrow is drought tolerant and butterflies are drawn to the flowers.
While not particularly edible, the way lettuce or spinach are, yarrow can be dried and used to make a tea. Young leaves and flowers are sometimes added to salads, but I just tried it and don’t care for it. The tea is very nice. Yarrow has been used as livestock feed, in some regions, and to some, it is a weed. Yarrow’s true value, however, lies in its role as an insectary.
Yarrow as insectary
Increasing the biodiversity in your garden or landscape helps to keep it healthier. Mutually beneficial arrangements that have taken millions of years to sort themselves out really are effective. Rather than trying to Disnefy your landscape, with neat and tidy arrangements, adding a variety of flower shapes, sizes, and colors will attract more beneficial insects. Okay, okay, so we all want the topiary elephant, but diversity is still healthier than monoculture. Yarrow flowers provide nectar and pollen to many beneficial insects, including:
Yarrow seeds need light to germinate, so do not bury them in the soil. A light dusting of soil or vermiculite will hold the seeds in place, but you might want to use a mister to water the seeds until the germinate. Either that, or you can saturate the soil with water, add seeds, and cover with plastic until the seeds germinate. Once your yarrow gets going, you will want to find it a permanent home. Yarrow tends to spread on its own, and it can even be used as a low border hedge. You can easily dig established plants up and divide them.
In the Bay Area, it is all too common to have areas of bare, hard-packed clay. This encourages erosion and unhealthy soil. Adding yarrow to your landscape or garden is a good way to reduce erosion, attract and feed beneficial insects, and hey, the flowers are lovely, too!
Chickens, jays, and mockingbirds can wreak havoc on your fruit and nut tree crops unless you provide protection.
Floating eye balloons, hanging old CDs, motion-sensing sprinklers, and noise cannons are just a few of the countless methods ‘guaranteed’ to protect your fruit and nut crop from marauding birds, but most of them do not work; not for long, anyway. Caging your tree is the only way to be sure that you get the lion’s share of your fruit or nut crop.
The netting used over your tree cage will still allow pollinators easy access. Unfortunately, it also allows codling moths and other flying insect pests to reach your fruit and nut trees. Even so, birds and squirrels can take a big bite out of apple, apricot, almond, nectarine, fig, and other crops. Tree cages can stop that damage before it even starts. Plus, these cages stay up, year round, so there's no wrestling with netting every spring and fall.
Store bought vs. DIY tree cages
Store bought tree cages can be astronomically expensive and most of the really nice ones are in the UK. The added shipping costs make it impossible or unrealistic for most of us. Luckily, it is surprisingly easy to make a tree cage yourself for less than $50. If you can scrounge old tree supports, it’s even cheaper.
Make your own tree cage
This tree cage design is intended for dwarf variety trees that will be pruned to 6 to 8 feet tall and 8 feet wide. You can adjust the measurements for bigger trees, but longer lodge poles can be harder to find and more expensive.
2. Using four lodge poles, flat on the ground, mark out an 8-foot (or smaller) square around your tree. On the inside of each corner, dig a hole at least one foot deep with the post hole digger. [If the ground is really hard clay, like mine, you can use a drill fitted with a large drill bit as an auger. It works surprisingly well.] Place one lodge pole in each hole and gently press the dirt you dug up back into the hole, making sure that the drilled hole runs outside to inside of the tree space, rather than side-to-side. You’ll see why in a minute. Also, dig one more hole to create the doorway space.
3. Take both 1”x2” boards and cut a 1/2-inch notch out of the middle of each, only cutting halfway through. I used a handsaw to make the perpendicular cuts and then a hammer and chisel to knock out the chad. Fit the 1”x2”s together in the middle and hammer together into a giant X-shape.
5. Staple 2’ chicken wire to the lodge poles, all the way around.
6. If you are really handy (which I am not), you can build yourself a fancy door. I opted for something far more simple: I cut a piece of bird netting that was larger than the door opening, attached it to the opening at the top, and ran a piece of thin scrap wood through the holes at the bottom. The wood weighs the netting down enough to keep chickens, mockingbirds, and jays away from my fruit and nut trees, and it’s easy to use. For added stability, you can add a cross piece above head height between one of the four lodge poles and the door lodge pole.
7. Drape bird netting over the X-shape and staple it down to make it taut. Ideally, you want birds and bats to bounce off, not get tangled. Bring the netting down over the sides until it reaches the chicken wire. You can use the wrapping wire from the roll of chicken wire (or string) to “sew” the netting to the chicken wire. I used heavy duty black thread and an embroidery needle.
If you like this design, please vote for it in the 2017 Garden Design Instructable!
Fruit. We all know what fruit is, right? Well, maybe not.
There are vegetables that we call fruits, nuts that are fruits, and fruits that are not fruits at all! Before we get started, let’s look at why plants go to all the trouble to produce fruit in the first place.
How fruit benefits a plant
In the world of plants, reproduction is the name of the game. Characteristics that evolve to promote the likelihood of a plant surviving are passed on to the next generation. Fruit is one of those characteristics. Creating fruit takes a lot of energy from a plant. But the fruit we eat has evolved to protect, disperse, and feed the seeds within. As the fruit ripens and falls, the fruit provides protection and nutrients. Fruit also encourages birds, animals, and people to spread seeds farther than the plant could do alone.
Depending on who you ask, fruits can be several different things. The simple tomato provides a classic example:
For something to be a botanical fruit, it must be the fertilized ovary of a flowering plant (angiosperm). After pollination and fertilization occur, two new structures are produced: seeds (fertilized ovules) and pericarp (thickened ovary walls). There are three different types of pericarp tissue: exocarp (outer skin), mesocarp (flesh), and endocarp (inner layer). The dominant pericarp tissue can become hard, as with nuts, or fleshy, as we see in peaches and avocados. In some cases, we eat the pericarp. In others, we eat the seed. When we eat the pericarp, we call it a fruit. Sometimes.
Like most things in life, the more we learn, the less simple anything is. Fruit is no exception. Fruits can be simple, multiple, or aggregate. Rather than going too far down that rabbit hole, let me summarize by saying simple fruits develop from a single ovary, multiple fruit forms when separate flowers cluster together, and aggregate fruits are clusters of multiple ovaries from the same flower. Make sense? Hang in there, it gets crazier! To start, fruits are also classified as either dry or fleshy.
Dry fruits are not the shriveled backpacking fare variety. Dry fruits are made up of dead cells that either split open (dehiscent fruit) or stay closed (indehiscent fruit). Dehiscent fruits include hazelnuts, walnuts, pecans, sunflowers, corn, and wheat. Indehiscent fruits include beans and peas, dill, poppies, and even cotton!
You might think you are finally in familiar territory, but that would be a mistake. The world of plant classification has been home to some bitter battles, and recent DNA analysis has turned many assumptions upside down. The fundamental categories of fleshy fruit are drupes, berries, aggregates, and multiples. Before you jump to any conclusions, check out these definitions for each category:
Nuts as fruits
Nuts are a strange case, when it comes to defining fruit. Some nuts are fruit, and some nuts are seeds. And some nuts, such as peanuts, aren’t nuts at all. Peanuts are legumes, which makes them indehiscent fruits. A ‘true nut’ is a hard-shelled pod that holds both the fruit and the seed, and the fruit does not open. True nuts include hazelnuts, acorns, and chestnuts. The other nuts are actually drupes. Drupes *dupe* us into thinking they are nuts, but they actually have a fleshy outer covering over top of the hard shell. Almonds, walnuts, and pecans are drupes, not nuts. But most of your friends will never believe you.
Accessory fruits and non-fruit fruits
There are also accessory fruits, which are made not just from the ovary, but also from nearby tissues. Common accessory fruits include strawberries, rose hips, apples, and pears. We may as well run the gamut with this one. Rhubarb is considered a fruit, but we only eat the stems, which are technically vegetables.
Getting the best fruits from your garden
Healthy plants produce bigger fruit. Keep your plants healthy with regular inspections for pests and diseases, appropriate watering and feeding, regular pruning, and disposing of mummies as soon as they are seen.
As your fruit starts to ripen, you can make it sweeter by reducing irrigation.
Why has someone wrapped the stems of our bananas? It’s all about the gas!
Bananas and many other fruits give off a gas as they ripen. This gas is called ethylene. Ethylene gas is also given off as a reaction to injury.
Often called the ‘ripening hormone’, ethylene gas is far more than that. It is a naturally occurring gas that regulates growth, development, and death of many different plants. When a plant is injured, ethylene gas redirects the plant’s biological activities to help it heal more quickly. Ethylene is what causes plants to die naturally. It also why your bananas turn brown when stored near apples.
Effects of ethylene gas
Ethylene is a small hydrocarbon molecule that stimulates the changes in texture, hardness, and color that we associate with ripening. Ethylene gas stimulates many other effects:
Ethylene gas is used in commercial agriculture to ripen fruit at a specific rate, so that they can pick and ship (flavorless) green fruit and then ripen it artificially. Anti-ethylene products are also used in agriculture:
Some fruits emit far more ethylene gas than others. Apples and bananas top the list. Other fruits that produce a lot of ethylene include:
Other fruits stored near near these ethylene producers will ripen faster that they normally would. Blueberries and cherries have very little ethylene gas, and no real impact. Some fruits and vegetables are particularly sensitive to the effects of ethylene gas. They will over-ripen and start to rot when exposed. These plants need extra protection:
Put ethylene gas to work for you
Placing a piece of fruit in a paper bag allows you to take advantage of ethylene gas. The paper holds the ethylene gas closer to the fruit, speeding the ripening process. Plastic bags do not work, as they trap moisture that can lead to rotting. To slow the ripening of neighboring fruits, many sellers place waxed cloth or plastic over the stem end of bunches of bananas.
Other sources of ethylene
Ethylene gas is not just from plants. It is manufactured for agribusiness. It is also the byproduct of your car’s engine, natural gas leaks, welding, and some manufacturing processes. The discovery of ethylene gas occurred over 100 years ago, when someone noticed that trees growing near gas street lamps kept dropping their leaves faster than other trees.
Maybe that’s why my store-bought strawberries go from nearly perfect to inedible overnight…
Catfacing refers to puckered ridges, filled with coarse brown skin, that can occur on your tomatoes, usually on the bottom. Cracking is something altogether different.
Catfacing is a physiological problem, believed to occur when the weather is cool and cloudy when blossoms emerge. Other damage to blossoms is also believed to cause catfacing. There isn’t anything you can do about it, but it might help you feel better to understand why it happens. Some varieties are more prone to catfacing than others. Catfacing does not change the flavor of your delicious tomatoes, but it does take away from the appearance.
Cracking occurs when a tomato’s inside grows faster than its outside. This can happen for a variety of reasons:
Irregular watering can also cause blossom end rot, so proper irrigation is always a good idea when growing tomatoes.
There are two types of cracking common to tomatoes: concentric and radiating.
Concentric cracks look like circles, starting at the stem end. These cracks heal quickly, protecting against insects and diseases with scar tissue. These tomatoes are still perfectly edible. Concentric cracks are common on fruit left on the vine after it has ripened completely. Harvesting regularly can prevent these types of cracks.
Radiating cracks usually start at the stem end and reach around to the blossom end. These usually occur just as the fruit is turning color. These cracks do not heal well, providing easy entrance to pests and diseases. If harvested right away, they are still edible.
Harvest to Table offers an extensive list of tomato varieties resistant to cracking and catfacing. Your best bet is to be very conscientious about watering your tomatoes regularly, especially in the peak of summer heat.
Furry carrots? Twisted roots? It might be aster yellow phytoplasma!
The bacteria that cause this disease reproduce in leafhoppers, root knot nematodes, and in the phloem of susceptible plants. These bacteria help leafhoppers and nematodes to live longer, but in our plants, the opposite it true. As bacterial populations grow, they block the flow of sap, water, plant hormones, and nutrients within our plants, causing chlorosis (yellowing) and distortion.
There is no known cure for aster yellows, so we have to look at the disease vectors: leafhoppers and root knot nematodes. Since leafhoppers can overwinter in weeds and perennial ornamentals, such as thistle, dandelion, black-eyed Susan, and wild carrot, keep these plants trimmed back from carrot planting areas. It’s probably a good idea to plant your beets somewhere else, too, since beet leafhoppers can be carriers. Bacillus thuringiensis (Bt) can be used to control these disease carriers. If an area becomes infected, avoid planting carrots there for a couple of seasons. Severe infestations can be dealt with using soil solarization, but that’s pretty drastic, since it kills everything in the soil, including beneficial soil microbes.
If you have deformed carrots, let’s just hope that is is caused by rocks or compacted soil, as those problems are much easier to fix. And, hey, those carrots can look pretty amazing!