You cannot see it, smell it, or taste it, but glomalin is the glue that holds soil together and the path by which nutrients move from beneficial fungi to plants.
When most of us think of fungi, we usually think of mushrooms or disease. Mycorrhizal fungi are an entirely different critter. These beneficial fungi live in soil, and in and around plant roots. They are responsible for helping over 70% of the Earth’s plants get the nutrients they need from the soil. They do this with glomalin.
Soil is made up of 45% minerals, 1-5% organic matter, 25% water, and 25% air, on average. Soil structure tells us the size of the mineral particles, which can be sand, loam, or clay. Air and water are found in tiny spaces, called macropores and micropores. The chunks of organic matter and minerals are called soil aggregates. Those aggregates are held together with glomalin. Soil aggregates improve water infiltration, drainage, nutrient cycling, root penetration, and water retention near roots. They also help counteract soil compaction.
Where does glomalin come from?
Glomalin is produced by mycorrhizal fungi that live in the soil and in, on, and around plant roots. Glomalin is found on the tiny hairs, or hyphae, of mycorrhizal fungi. This coating helps the fungi to retain water and nutrients as they interact with local plant root systems.
What is glomalin?
Glomalin is a tough, resilient glycoprotein that contains significant levels of iron. It does not dissolve in water and it is resistant to decay. Also known as glomalin-related soil proteins (GRSP), glomalin stores carbon and nitrogen, and binds mineral particles together, coating them with the same protective barrier used to protect the fungi. It is now believed that 15 to 20% of the carbon sequestered in undisturbed soil is held specifically by the glomalin. This is one of the reasons behind no-dig gardening, in that it reduces the negative impact on the fungi responsible for creating glomalin and helps the soil hold onto that carbon.
How does glomalin improve soil quality?
Glomalin was discovered in 1996 by Sara F. Wright, a USDA Agricultural Research Service scientist. She discovered that soils depleted of mycorrhizae and their glomalin, whether through exploitation, solarization, or fungicide use, had significantly reduced crop sizes.
Glomalin helps hold organic matter in place, improving soil aggregate stability. Soil aggregate stability is a measure of the combined physical, chemical, and biological properties of a soil sample, as well as its ability to resist degradation and erosion. Without glomalin, every drop of rain and every gust of wind would grind and disperse soil in a global Dust Bowl.
Glomalin is also what gives soil its brown color. Removing glomalin from soil leaves it a grey, rocky color.
So, what’s glomalin to you?
Recognizing the importance of mycorrhizal fungi and glomalin to soil health, you can improve plant and soil health with these tips:
By keeping your soil healthy, the natural processes needed by your plants to acquire nutrients and fight disease can continue.
Zebra chip may sound like a fun new black-and-white striped snack, but it’s not.
Zebra chip is a bacterial disease that attacks potatoes.
Like most bacteria, Candidatus Liberibacter solanacearum doesn’t move around very well on its own. Instead, it lives in the gut of potato psyllids. Potato psyllids are tiny, sap-sucking pests. As they feed, the bacteria move from the insect to the plant, infecting the vascular tissue in both the plant and its tubers.
Symptoms of zebra chip
There are no aboveground symptoms of zebra chip, but potato psyllid feeding causes foliage to turn yellow or purple. It can also cause pink or red discoloration of leaves.
The real symptoms are visible only after you cut into a tuber. The zebra chip bacteria cause potatoes to store sugar, rather than starch. That might sound like a great idea for a new dessert food, but the presence of sugars cause vascular tissue to turn into ugly brown lines. When cooked, these brown lines turn black, hence the name. This condition also reduces crop size by 20 to 50%. Healthy appearing potatoes from plants affected by zebra chip are more likely to sprout while in storage. Seed pieces taken from infected plants either do not sprout at all, or they produce weak, infected plants.
Controlling zebra chip
Since zebra chip is carried in by potato psyllids, that’s where you must work to break this disease triangle. Potato psyllids can be trapped with yellow sticky sheets and spinosad can be used to reduce potato psyllid populations. These treatments won’t get rid of all the psyllids, but they will help. Be sure to inspect potato, bean, and pepper plants regularly for signs of psyllids.
In commercially grown potato fields, where potato psyllids have been identified, a type of systemic neonicotinoid neurotoxin, called imidacloprid, is applied. [While not yet noted in California, resistance to imidacloprid has been documented in Texas.]
Zebra chips might sound like a fun new brand of potato chips, but what they really mean is you need to be on the lookout for potato psyllids as you work and play in the garden.
In the short days of winter, many of your fruit trees look as though they aren’t doing much of anything. Other than collecting chill hours and working to stay alive, that would be mostly true. As the days begin to lengthen, leaf and flower buds start to swell. But, sometimes, those swellings are something else entirely.
Also known as the almond and plum bud gall mite (Acalitus phloecoptes), this pest is native to Europe and the Middle East. As of January 2019, it made its way to California, threatening tens of thousands of plum, pluot, almond, apricot, and many other fruit and nut trees.
What are plum bud gall mites?
Plum bud gall mites are a type of eriophyid mite. Eriophyid mites are a family of microscopic plant parasites. These pests enter stems and buds through lenticels and injury points, and then overwinter under the bark. Very little information is available about this new pest, but knowing what to look for can help you to stop it from spreading.
Plum bud gall mite identification
In late winter, galls begin to form around these tiny invaders. By spring, adults emerge from their protective galls. At 1/100th of an inch in length, these mites are too tiny to see with the naked eye. If you have a 20x hand lens, you may be able to see them, if you look very closely. They can be a translucent yellow, pink, white, or purple, with two pairs of legs up near the head. You are more likely to see galls on new shoots and fruit spurs that plants produce in response to these invaders. Galls are warty, bumpy growths that don’t look like normal tissue.
Controlling plum bud gall mites
Treating your trees with wettable sulfur in March or April, when plum bud gall mites first start to emerge from their protective galls, has been effective in controlling these pests in other regions. Treatments may need to be repeated, depending on the level of infestation. Note that apricot leaves are very sensitive to sulfur, so you can only treat apricot trees with sulfur before leaves emerge. Because these particular eriophyid mites are new to the region, we do not yet know what sort of an impact native predatory insects will have on controlling plum bud gall mite populations.
If you happen to see this new pest on your trees, please contact your County Extension Office right away.
Each spring, pollen grains are normally moved from flower to flower by honey bees, beetles, butterflies and moths, and wind. When the pollen arrives at another flower, fertilization can occur and fruit can grow. Except, sometimes, the pollen needs a little help. That’s where hand pollination comes in.
Plants being grown indoors, or in areas without enough bees and other pollinators, cannot set fruit without mechanical pollination. Some crops, such as cucumber, melon, pumpkin and other squash, can be coaxed into producing far more fruit if hand pollination its used, due to the timing issues related to male and female flowers occurring at different times.
If you grow plants indoors, you will need to pollinate the flowers by hand to get fruit. Container plants that are at a distance from their fellows will also benefit from hand pollination. Loquats, kiwifruit, and mangos, in particular, often require hand pollination. [Due to heavy pesticide use in China, the lion's share of all their fruit crops are now pollinated by hand.]
Hand-pollination is not difficult, but it is tedious. To better understand how hand pollination works, let’s have a quick review of flower anatomy and the pollination process.
For a more detailed description, I urge you to read my posts on flowers and pollination. In the most basic terms, flowers can be male, female, or both, but not necessarily at the same time. Male flowers have a stamen and female flowers have a pistil. The stamen consists of a pollen-producing anther at the end of a filament. Pollen tends to be yellow and sticky. The female pistil, also known as a carpel, is usually found in the center of a flower and it consists of the sticky stigma, which captures pollen, the style, a tube that leads to the ovary, and the ovary itself.
As insects move around, collecting nectar and pollen for themselves, sticky pollen becomes attached to their legs and is carried from flower to flower. The pollen is captured by the stigma, enters the style, and moves toward the ovary, where fertilization occurs. If there are not enough pollinators, the pollen doesn’t get moved and we have no fruit. Unless you hand pollinate. By hand pollinating, you become the mechanism by which pollen is moved from the stamen of the male flower to the pistil of the female flower.
How to hand pollinate
There are two basic methods of hand pollination: removal of the anther, or transferring just the pollen. In most plants from the cucurbit family, the male anther is large and obvious. Without handling the part covered with pollen, simply snip off the anther, cut off or roll back the flower petals, and gently roll it around on the female pistil.
On plants with smaller flowers, such as cucumber, tomatoes, and melons, you can use a small, natural bristle painter’s brush or a cotton swab to transfer pollen from one plant to the other.
Timing is important
Male flowers tend to emerge before female flowers. Also, most flowers are only receptive to pollen for one day. Transfer pollen to freshly opened flowers, preferably in the morning. Do this every day until fruit starts to form.
Concerns about cross-pollination
This comes up every year. People worry that all members of a group, such as the cucurbits, can cross-pollinate. They can’t. Melons, squashes, and cucumbers are too different from one another to pollinate each other. That being said, varieties within a species, such as white pumpkins, Jack O’ Lantern pumpkins, and Atlantic Giant pumpkins can cross-pollinate.
Even if you have bees in your garden, you may want to try hand pollinating. Research has shown that manually applying pollen to female flowers results in larger fruit that is more likely to reach maturity. Also, the seeds within that fruit germinate faster and produce larger seedlings. This is called the xenia effect.
Did you know that researchers at Harvard are creating miniature flying robots, called RoboBees, to be used as pollinators?
Now you know.
Throughout human history, early spring has always been a time for eating fresh new greens. Slightly bitter, rich in iron and other important nutrients, they remind us that winter will not last forever.
Patience dock growth
Patience dock plants start out as broad leaves growing close to the ground. This is the part you want to eat. Next, a single stem emerges and is quickly covered with tiny flowers. Those flowers become pollinated and fertilized to produce triangular seeds, similar to rhubarb seeds. Seed heads hold large numbers of seeds, which darken to a lovely bronze color.
How to grow patience dock
Seeds are generally planted in late spring, slightly less than 1/2 an inch deep, in locations that receive lots of sunlight. Plants should be thinned or transplanted to provide at least 8 inches of space between plants. Lucky for those of us in the Bay Area, patience dock thrives in heavy clay soil. Young plants will require frequent watering, but mature plants require far less. If grown in a container, patience dock plants should be repotted each year with fresh potting soil, or mulched regularly with aged compost. Once established, plants are highly resistant to frost damage. You can divide mature plants every 3 to 4 years, in spring, to generate new plants.
While it might be easier to list the plants not susceptible to beet armyworms, you need to know where to look for these pests. In addition to beets, the list of potential beet armyworm hosts includes beans, celery, cilantro, citrus, cole crops, cucurbits, lettuces, parsley, peppers, strawberries, and tomatoes. Beet armyworms also attack alfalfa and cotton.
Beet armyworm lifecycle
Female moths lay pale, pinkish or greenish striated eggs in clusters of more than 100 eggs, often on the upper sides of leaves. These clusters look fuzzy, due to hairlike scales left behind by the moth. After they hatch, larvae begin feeding on nearby leaves, slowly dispersing throughout the plant. As larvae get older, they also feed on fruit. After defoliating your plant, the mature larva drops to the ground, where it pupates in a shallow depression in the soil, or in a pocket excavated just below the soil surface. An adult moth emerges, and the whole process begins again. This cycle is completed in one month, so there can be multiple generations each year.
Beet armyworm description
Larvae are smooth, pale green caterpillars, with several pale, wavy lines down the back and a broad stripe down either side. You may also see a dark spot above the second pair of legs. Other color variations can occur, depending on the food source and developmental stage. After 2 or 3 weeks of feeding, caterpillars will reach 1.25 inches in length. Adult moths are mottled brown and grey, with a 1-inch wingspan.
Damage caused by beet armyworms
Beet armyworms can destroy seedlings in only minutes. When feeding begins, the damage appears as clusters of circular or irregularly shaped holes in leaves. It can also cause flagging, a condition that slows or halts growth on one side of a plant. Larvae will feed on the crown of lettuce plants, killing them. As caterpillars get bigger, they can skeletonize all the leaves on a plant. Most fruit feeding occurs on or near the surface, and can be cut away, assuming other pathogens haven’t entered the fruit, causing disease or decay. Of course, you will want to wash the fruit thoroughly, to get rid of caterpillar feces. If beet armyworms feed on floral buds, the buds will abort.
How to control beet armyworms
In the home garden, natural predators are your plants’ best defense against beet armyworms. Predatory wasps will parasitize beet armyworm larvae, while big-eyed bugs, and minute pirate bugs will feed on the eggs. Spiders, damsel bugs, assassin bugs, tachinid flies, and lacewings will also feed on beet armyworms, so avoid using broad spectrum pesticides. In severe cases, you can apply spinosad or a specific type of Bacillus thuringiensis (ssp. aizawai).
Prevent beet armyworm invasions by monitoring nearby weeds, especially lambsquarters, goosefoot, and pigweeds for signs of egg clusters.
Harvesting your crops as soon as they are ready can also interrupt the lifecycle of these pests.
Beet armyworms have been known to travel as far as 10 feet during a night, putting most of your garden plants at risk. Monitoring for signs of beet armyworm infestation can help you prevent the problem from spreading.
Today, we are looking at some cutting-edge research in the world of plants. It may not make you a better gardener, but you’ll know more about plants than pretty much everyone else, and you may look at your plants a little differently.
Imagine, if you will, a tiny plant cell. Within that cell is a bubble of fluid, called a vesicle. Vesicles form naturally as plant cells eat and poop and go about their business. You can think of these bubbles as microscopic burps that stick around. Plant cells can also create vesicles on purpose. When this happens, they are called liposomes. [Keep in mind that this is an extreme oversimplification of what is actually going on, but you’ll have the basic idea.] A plant cell may have several vesicles, which cluster together into groups, called multivesicular bodies (MVB).
Vesicles are extremely small. They range in size from 30 to 150 nanometers (nm). A nanometer is one billionth of a meter. By comparison, plant cells range from 10 to 100 micrometers, while animal cells can be 10 to 30 micrometers. Micrometers (μm) are one millionth of a meter. A strand of human hair ranges from 17 to 181 µm.
Ergo, one human hair = 10 plant cells = 300 vesicles
What do vesicles do?
Plant cells use vesicles to move materials around, process proteins, maintain buoyancy, and all sorts of other things that we are only now learning about, though scientists have known about the existence of vesicles for a while now. What we didn’t know, until very recently, is that plant vesicles perform the same function as a type of animal cell vesicle, called an exosome, does. Their job is to take material from the interior of the cell, attach itself to the inner plasma membrane, create an opening, and then release the material into the apoplast, which includes the cell wall and the space between cells. Fungal cells do the same thing, but we didn’t know plants did until very recently.
In animal cells, there are specialized vesicles that check the load being carried by other vesicles, to see if the contents should be destroyed or moved to the apoplast. Plant cells do not have those specialized gatekeepers, so there is still plenty to learn.
Now, this may not sound like a Big Deal, but this is how cells communicate with each other, triggering plant growth and defensive measures. In fact, exosomes are directly related to the production of defensive proteins and RNAs used to fight disease. Exosomes are also used to move those defensive proteins from nearby healthy cells to a cell under attack by a pathogen, to create protective barriers against disease, and they can even enter invading cells to inhibit their growth. [If you are interested in this sort of thing, it is called host-induced gene silencing.] On the down side, exosomes also play important roles in malignancy.
In the not-too-distant future, we may be seeing artificially generated plant exosomes crafted to boost our plants’ ability to fight disease. Similar studies are being conducted to see if plant exosomes can be used in human medicine, such as exosomes found to reduce alcohol-induce liver damage in mice, or how vesicles of the ginger plant may be able to reduce inflammation in the human digestive system. For now, I will stick with ginger tea, but maybe exosomes were the reason it has been helping all along…
Bee's friend is a gorgeous flower that attracts pollinators and other beneficial insects
Also known as blue or purple tansy, or lacy phacelia, bee’s friend (Phacelia tanacetifolia) is a popular choice in agriculture as an annual ground cover. It is also grown as an insectary, to attract bees and beneficial predatory insects, such as hoverflies. Flowers remain open for an extended period with very little water, making it an excellent addition to your foodscape.
Bee’s friend description
Single, mostly unbranched, stems of bee’s friend can reach 4 feet in height, but most plants are only half that height. Curled leaves and stunning lavender-blue flowers make this a uniquely attractive plant. Most domesticated varieties are smooth-stemmed, while wild varieties are covered with stiff trichomes (hairs).
How to grow Bee’s Friend
Bee’s Friend seeds can be sown directly in areas that receive direct sun or partial shade, as soil temperatures warm in late spring. Stagger plantings for a more powerful impact. Seeds must be in complete darkness to germinate, so be sure to follow the planting directions on the packet and use an irrigation method that does not push the soil around too much. Misting is a good choice
Bee’s friend is considered one of the top 20 honey-producing flowers. Whether you raise bees or not, that much nectar is sure to bring bees and other pollinators to your garden in abundance! It makes an excellent plant for under or around fruit and nut trees, as a natural way of boosting pollination rates. The flowers are lovely, too!
We’ve all heard about butterfly gardens and herb gardens, but what about pizza gardens, or sunflower forts?
One of the many attractions of gardening is that you can play with it. We are not limited to the furrowed rows of earlier generations. You can be as creative as growing conditions and your plants’ needs will allow. And deciding on a theme is a way to pull your garden together artistically or aesthetically.
Themes provide a unifying framework, a story, a uniqueness to your garden, and they can be a lot of fun. Themes are more artistic than simply how you grow your plants. Garden themes make it easy to decide on which plants work best in a landscape, a raised bed, or even a single container, by providing a long term, broader perspective on that space.
You can create a theme based on flower color, leaf shape, or even a particular shade of green. You can create a theme that takes advantage of a shady corner, transforming it from a seldom used, mostly wasted space into a storybook hideaway, complete with peek-a-boo elf statues and a reading chaise lounge. [More lemonade, please!] Or, you can create a theme around a favorite book or movie.
Garden themes can be whimsical, or they can be utilitarian. Let’s take a look at some examples of each type:
Gifts garden If you like to give plants as gifts, plan ahead for that. Create a nursery bed specifically for plants to be given as gifts. You can find more tips on this winning garden theme in my post titled Planting Backwards.
Holiday dinners garden Nothing says gardener like fresh Brussels sprouts and baby beets at Thanksgiving, fresh greens at Easter, and a juicy watermelon on July 4th. Planning your planting to coincide with harvests when you are going to want them makes a holiday dinner garden a handy theme.
Pollinator garden Attract beneficial pollinators with a patch of garden dedicated to everything they love, want, and need. Nectar-producing flowers that come in a wide variety of colors and shapes, a nice layer of mulch, and a water source will draw them like flies, where they will stay to pollinate all of your garden crops.
Salad garden Keep yourself in salad ingredients with a continuous supply of spinaches, lettuces, Swiss chard, scallions, peppers, or whatever you prefer in your salad. Growing these healthy ingredients in close proximity adds color and texture to a garden patch, along with convenience for your dinner table.
Tea garden You don’t need to provide the exquisite care needed for a traditional Japanese tea garden to grow plants that taste delicious when steeped in hot water. Peppermint, chamomile, lemon balm, turmeric, garlic, and sage are all easy to grow and can provide a perpetual free source of tea for family and friends.
Those garden themes are all very useful, and they make plant selection simple. But what about some of the more fun ideas? My three favorites are children’s gardens, corn and sunflower forts, and pizza gardens:
Children’s gardens Children love plants they can touch, taste, and smell. Feathery soft yarrow, creeping chocolate mint, and towering fronds of licorice-scented fennel all come to mind for a children’s garden. Also, children need plants that grow quickly. Radishes and beans are always good choices. [You may be surprised to discover that most children love the taste of spinach they have grown themselves…]
Corn and sunflower forts The soaring heights of corn and sunflowers makes these plants perfect for forts and mazes. Simply draw where you want the walls to grow, plant seeds, and top dress the area, watering as needed. You will have to provide protection from feet and paws, at first, but, before long, they will support each other as they grow ever higher. You can even add nice little touches, such as a climbing cucamelon or purple pole beans.
Pizza garden You can set aside a piece of garden for a specific meal. In this case, you can plant tomatoes, peppers, onions, garlic, oregano, basil, thyme, and whatever other herbs and vegetables you enjoy on a pizza. Heck, if you have a 9-foot square space, you could even grow the wheat for your pizza crust! Of course, the garden can’t help with the cheese or pepperoni, but you get the idea.
Garden themes require the gardener to look forward in time. Being the optimists that most of us tend to be, this isn’t hard to do. That’s why we keep putting seeds in the ground, year after year, we know that most of them will grow.
Now, you can stop letting your preconceived notions of gardening stop you from trying something different and unique. Go ahead! Have fun with it!
What kind of garden theme are you going to try?
You can grow a surprising amount of food in your own yard. Ask me how!