Boing! A tiny insect launches itself and you never really see it clearly.
It’s probably a leaf hopper. Let’s learn about these garden pests so we can reduce the damage they cause.
Leafhoppers are cousins to treehoppers and cicadas. The name “leafhopper” actually refers to twenty thousand different Cicadellidae insects. Most leafhoppers feed on a specific plant or group of plants. Eggs are laid in soft plant tissue, where they overwinter. Eggs begin to hatch in mid-April in the Bay Area. These wingless nymphs will molt several times, each time their wings and hind legs getting larger and more functional. What makes leafhoppers particularly unique is that they cover themselves, after each molt, with a microscopic body armor made out of netted spheres called brochosomes. [It's one of those 'stranger than fiction' realities, isn't it?]
This armor keeps them dry and protects them from their own sugary excrement. Brochosomes are also believed to protect them from enemies, as well, but no one is really sure. What I am sure of is that leafhoppers are unwelcome in my garden and landscape, and here’s why:
Leafhoppers eat sap and, as they feed, they spread disease.
Plants preferred by leafhoppers
Leafhoppers enjoy many of the same plants that we do. In addition to many woody ornamentals, such as boxwood, local leafhopper species love to feed on sweet potatoes, squash, beans, horseradish, cucumbers, corn, melons, blueberries, grapes, and beets, just to name a few! Since leafhoppers can carry diseases with them, they put many plants at risk.
Leaf stippling is usually the first sign of leafhopper infestations. This damage is normally at its worst in July and August, in the Bay Area. While leaf stippling won’t harm a healthy plant, it does interfere with photosynthesis and it can compound water stress. Leaves may also appear pale or brown, and new shoots may curl up and die. As they feed, some leafhopper species produce honeydew, which provides the perfect growing medium for sooty mold. Also, leafhoppers are vectors for several plant diseases, including aster yellows, bean mosaic, and vivipary.
Since they are so mobile, complete control is pretty much impossible. Spiders, assassin bugs, and lacewings all eat leafhoppers, so avoid using broad spectrum pesticides that will kill off these beneficial insects. Severe infestations can be treated with insecticidal soap or horticultural oil, just be judicious with the application since oils can contribute to sunburn damage. These treatments are only effective on nymphs.
So, if you walk by a plant and get pelted by a bunch of tiny bugs, or you notice a lot of leaf stippling, take a closer look - it may be time for a spray of soapy water.
Few plants are as productive as summer squash. They grow quickly, provide a continuous harvest, and they shade the ground under their prickly leaves, making it an excellent foodscape plant.
Summer squash vs. winter squash
All squash plants are cucurbits, along with gourds and cucumbers. Squashes are classified as either summer or winter varieties. The main difference between summer squash and winter squash is when it is eaten. Summer squashes, which are generally eaten immature, have thin, tender skins, while winter squashes have hard skins that allow them to be stored for longer periods of time. Common winter squashes include pumpkins, Hubbard, acorn, and butternut squash. There are two main types of summer squash: zucchini and yellow, but these are divided up into several different varieties:
How to grow summer squash
Summer squash prefers a sunny, well drained area, with a pH of 5.5 to 6.5, so acidification may be needed. Squash seeds are very large and should be planted about an inch deep in May and June. [The basic rule of thumb for the planting depth for any seed is to use the longest length measurement of the seed and bury it that deep.] Keep the soil moist until germination occurs, but do not let it stay soggy or damping off disease may kill your squash seedlings. Squash plants generally do not take kindly to transplanting, so it is better to plant the seeds where you want them in the first place. These plants will take up some space, though they can be grown in containers, towers, and straw bales, and they love raised beds! Squash is a traditional member of the Three Sisters Method of growing beans and corn in a mutually beneficial garden design. Generally, winter squash vines can get very long, while most summer squashes have more of a mounding growth, though this isn’t always the case. Be sure to read the seed packet for variety-specific information. Squash is a relatively light feeder, so fertilizer is rarely needed. These plants generally get enough nitrogen from the soil. Too much nitrogen will encourage plenty of leaves but very little fruit. Of course, adding some aged compost around the plants as mulch certainly wouldn’t hurt!
Summer squash pests and diseases
If you look at a list of all the pests and diseases that affect summer squash, you’d wonder how these plants survive at all. But they do. In fact, they thrive! But it’s always a good idea to know what might happen, so you can nip it in the proverbial bud before things get out of hand. Common summer squash pests include aphids, armyworms, cutworms, redhumped caterpillars, leaf miners, loopers, cucumber beetles, nematodes, grasshoppers, slugs and snails, stinkbugs, wireworms, earwigs, and various beetles. Squash bugs are generally your biggest threat and they make themselves known in July in the Bay Area. As far as I know, squash vine borers have not yet made their way over the Rockies, but be forewarned! Row covers go a long way toward protecting your summer squash plants against these pests. Summer squash diseases can categorized by the pathogen:
Environmental conditions, such as irregular watering, can cause blossom end rot, bitter fruit, and blossom drop. Poor pollination can also be a problem. Despite all these threats, summer squash plants nearly always produce an astounding amount of food.
Harvesting summer squash
Squash plants can run amok and get away from you. Everyone has a story of the monstrous zucchini they swore wasn’t there the day before. It happens. When it does, stuff it with sausage and onions, or make some Chocolate Zucchini Cake. One nice thing about summer squash is that it can be harvested at any stage in its development. Simply cut the stem and enjoy the fruits of your labor! Once you’ve harvested a summer squash, you can add it to stir fry, salads, soups, stews, or just nibble on it while reading a good book. Odds are, another one will be ready to harvest in a day or two. Summer squash is particularly sensitive to ethylene gas, so you will want to keep them away from bananas and other ripening fruits.
One seed and a little water can provide you with a surprising amount of fresh food. Plant one today and see what happens!
Marjoram is the soft-spoken cousin of oregano.
Marjoram is a tender perennial herb that can do well on a window sill, in a tower or other container, or tucked away in a quiet corner of the garden. These plants also make nice rock garden additions and they look (and smell) lovely next to walkways and in parterres. The Greeks and Romans used marjoram as a symbol of happiness, and it certainly puts a smile on my face whenever it turns up in my foodscape.
Uses for marjoram
Marjoram leaves have been a culinary herb for a very long time. It is slightly more mild and piney than its boisterous cousin, oregano. Marjoram is used to make herbes de Provence and za’atar. Marjoram also attracts many beneficial insects, including butterflies and bees, with its tiny white, pink, and lavender flowers.
An herb by any other name
Marjoram (Origanum majorana) has been around long enough to have several names to differentiate it from oregano (Origanum vulgare), including sweet marjoram and knotted marjoram. Oregano is also known as wild marjoram. Other varieties of marjoram include:
Marjoram is best started in pots. Seeds should be covered only lightly with soil. Keep the soil moist until seeds germinate, being careful not to wash them into a corner of the pot with miniature floods of water. Marjoram prefers full sunlight and loose soil. Plants should be hardened off before installing outside, and spaced 18 inches apart. Marjoram and oregano are both members of the mint family. As such, they tend to spread underground using rhizomes. This makes them a good ground cover plant, as well. Marjoram has semi-woody stems that lend themselves nicely to cascading out of hanging pots, or as a low shrub. While technically an evergreen, cold temperatures will cause them to lose their leaves and frost will kill the above-ground portion. One way to protect your plants and keep the garden attractive in winter is to cut the plants back to ground level and cover with a winter blanket of mulch. Come spring, those delicious new leaves will come right back for another year. Luckily for those of us in the Bay Area, marjoram prefers alkaline soil, which we have in abundance. Marjoram never needs fertilizer when grown in the ground, and it rarely needs watering once established.
Marjoram pests and diseases
I have found whiteflies and spider mites to be the biggest problems for marjoram. Those tiny sap suckers leave behind speckled, bleached out leaves that don’t look at all appetizing. You can fight back with a spray bottle filled with soapy water or diluted horticultural oil. (Dormant oil is too heavy.) Aphids, cutworms, mealybugs, and thrips may also try feasting on your marjoram plants, but a forceful spray of water can every morning can usually displace most of these pests. Though rarely affected, fungal diseases such as dodder, damping off, downy mildews, powdery mildew, rust, and botrytis blight (grey mold), can occur on marjoram.
How to harvest marjoram
Just as your marjoram plants begin to flower, snip off the upper portions and hang them in a shady spot to dry. Garages work well. Guest room closets work even better. I like to believe that the gentle aroma helps guests enjoy a restful sleep. That might just be me.
Try adding marjoram to your garden or landscape today for many years of fragrant, delicious beauty.
Flies swarmed over my ornamental shrub and I was confused. One expects to see flies collecting around, well, around less desirable resting spots. I have dogs and chickens, so there were plenty of other, more odiferous opportunities, but the flies clearly were more interested in my shrub. What was going on? Let’s find out.
Crane flies, dragonflies, butterflies, fruit flies, whiteflies, hoverflies, you’ve heard plenty about these flying insects in the garden, but what about the lowly housefly? It turns out, houseflies (Musca domestica) are not necessarily the pests they have always been made out to be, not completely anyway.
True, nobody wants a fly landing on their food. There’s too many awful places they may have been. Those hairy legs of theirs may have been walking around in some nasty messes. You may be surprised to learn, however, that one of the most common places to find houseflies… is in the flowers of your garden.
The nature of flies
Most flying insects have four wings. Flies only have two. True flies are all members of the Diptera family. Unlike busy bees and industrious ants, most fly species are lazy. They are mostly meat eaters. They also feed on manure, rotting stuff, and even open wounds. (Ew!) What you may not know is that flies also enjoy cleansing their palettes with a sip of nectar now and then. When flies land on a flower for a sweet sip, their hairy/spiky legs collect pollen. Most of them don’t eat the stuff, or hoard it, the way bees do. It just sticks to them. When they fly to their next sipping/resting spot, the pollen goes with them and often pollinates that flower. The process continues at a surprising rate. It ends up that flies are probably one of the first pollinators of flowering plants.
Bees vs. flies as pollinators
We all know about honey bees pollinating our crops: the bees go from flower to flower, collecting nectar and pollen and they transfer the pollen to other plants, leading to pollination, fertilization, and food for us. The problem with bees, as pollinators, is exactly that - they take the pollen with them. Eventually, there is no more pollen in a particular flower. That means bees can visit a flower and not pollinate it. Flies, on the other hand, generally do not eat pollen, so there is more left behind as they move from flower to flower, looking for a place to rest and have a drink. In a study conducted by the North Central Region Plant Introduction Station (NCRPIS), it was shown that adding blue bottle flies (Calliphora sp.), along with honey bees, as pollinators, carrot production was significantly increased. Also, flies are active within a wider temperature range than honeybees.
Crops commonly pollinated by flies
There are a surprising number of crops regularly pollinated by flies, besides members of the carrot family. These include apples, raspberries, strawberries, pear, plum, cherry, peach, nectarine, blackberries, and pawpaw. There is a group, called flower flies (Syrphidae), that pollinate dozens of our food crops. One particular species of fly, Ornidia obesa, is the reason we have chocolate. Yes, I said it. Flies pollinate cocoa plants.
Flies may not pollinate as many crops as bees, but they are already a close second, and that claim is made with only minimal research. We may find they are responsible for far more pollination. That being said, flies can also carry disease. They are free to roam my garden and landscape, but my patio is draped overhead with fly paper. Simple, yet effective.
Chenopods include edibles such as California goosefoot, amaranth, and quinoa.
UPDATE: Until recently, chenopods were considered a distinct plant family. Genetic testing has altered that status forever. Chenopods are now recognized as members of the amaranth family (Amaranthaceae).
Many chenopods are considered severe agricultural pests, and the pollen from all of these plants can cause an allergic reaction for some people. Flowers generally bloom from spring through fall, but we can enjoy the benefits provided by some of the more benign varieties without adding invasives into our gardens and landscapes.
The Chenopod tribe
Russian thistle, waterhemp, pigweed, and kochia are all chenopods. Plants in this group can be annuals or perennials. They may be herbs, shrubs, or even trees. And they may grow in an erect or prostrate manner. In other words, chenopods have evolved in many different ways. Scientists are still debating chenopod classification, but we will leave that to them. Collectively, chenopod branches are alternate (which means they take turns up a stem), the leaves have petioles (tiny stems) and are shaped like a goose’s foot; hence the name ’cheno’, which means goose, and ‘pod’ which means foot. Young leaves and stems are often covered with tiny hairs (trichomes) or a white mealy dust, a condition called farinose. Humans have been eating chenopods for over 6,000 years. Below are some of the more common chenopod edibles.
Chenopod pests and diseases
Birds and butterflies enjoy eating the seeds, but these plants continue to survive and thrive, so the damage can’t be all that significant. The same holds true for apple stem grooving virus, tobacco necrosis virus, and the cowbane mosaic virus. They try to slow these plants down, but generally cannot.
Find a sunny spot in your garden or landscape for these colorful edibles!
Belly rot looks almost as bad as it sounds.
What starts as brown or black mushy areas on the underside of your melons or squashes turns dry and leathery. It won’t hurt you, but it can make fruits more susceptible to other pests and diseases.
Melons, squashes, and other members of the cucurbit family can all get belly rot. Belly rot is a fungal disease caused by Rhizoctonia solani. Infection occurs when fruit is left to sit on the soil for prolonged periods, especially when moisture is present.
Symptoms of belly rot
If you see water-soaked, sunken, black or brown spots on fruit, and it is not blossom end rot, it is probably belly rot. The lesions can be very small to covering the complete underside of a fruit. As the infection spreads, the lesions dry out and become leathery or scabby. Infected fruit should be removed
Preventing belly rot
To prevent the spread of belly rot, avoid overhead watering and get that fruit up off the ground. You can use trellising, tomato cages, children’s furniture, those little plastic pizza box props, straw, benches, colanders - ANYTHING that will allow some air to get between the fruit and the soil. Improving drainage will also make this disease less likely to occur.
Generally, the fungi that cause belly rot are everywhere, so prevention is your best bet. This means checking the bellies of your melons on a regular basis!
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 with 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° 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 black 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 irrigation rings. Irrigation 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 nodes 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…
You can grow a surprising amount of food in your own yard. Ask me how!
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