Glyphosate is an herbicide. It is the active ingredient in RoundUp and other popular broadleaf weed and grass killers. And recent scientific research has shown us that glyphosate may be killing honey bees along with plants.
Before we begin learning about this litigious herbicide, let me tell you from the gate that I do not use it, in any form. I practice sustainable, integrated pest management (IPM) and organic gardening. This is a heated topic and I want you to be aware of where I stand.
The chemistry of glyphosate
Glyphosate is a broad-spectrum, systemic herbicide, which means it is absorbed by and kills the plants it touches. It does this by blocking an enzyme pathway, called the shikimic acid pathway. [It gets this unique name from the Japanese shikimi flower, in which the process was first identified, back in the 1800s.] The shikimic acid, or shikimate, pathway is a 7-step metabolic process that synthesizes folates and amino acids necessary for plant survival. Herein lies the problem. The shikimic pathway is also used by algae, bacteria, fungi, protozoa, and others. When the shikimate pathway in any of these organisms is blocked, they die.
Glyphosate in the environment
More that 700,000 tons of glyphosate are produced each year, making it the world’s most used pesticide. As a substance, glyphosate molecules bind tightly to soil. While this means they are less likely to end up in ground water as, say, motor oil, it can cause a different type of pollution. Depending on soil type and weather conditions, glyphosate can be found in the soil 6 months after being applied. Soil bacteria break down glyphosate, but I have to wonder about the chemicals those bacteria poop out afterward. Maybe it’s just me. Some studies have found that carrots and lettuce plants absorb glyphosate long after the area was treated. Compounding the problem, many glyphosate products also contain other toxic ingredients.
Glyphosate and GMOs
Glyphosate use walks hand-in-hand with genetically modified plant development. GMOs are designed to be resistant to glyphosate and other weed-killing chemicals, making it possible to grow more food for our ever-increasing global population. It certainly has its appeal. It’s so simple - just aim, squirt, and you’re done. No more weeds. But at what cost?
Glyphosate and overspray
If you (or your neighbor) use a glyphosate product, you need to be aware of the overspray risk. Since none of us is perfect, and breezes do happen, these chemicals can be carried on the wind to places where they are not welcome. That delicate, well loved exotic, handed down from your great-grandmother, is just as vulnerable to death by glyphosate as the dandelions. Also, since glyphosate products kill all the plants it touches, indiscriminately, many plants important to local biodiversity are being lost. We do not yet know the full extent of that domino effect.
Glyphosate and bees
Beekeepers have long suspected that glyphosate is, at least partly, responsible for the recent decline in global bee populations. [Did you know that China now must hand-pollinate their apple and pear trees because there are not enough bees?] New research from the University of Texas at Austin shows that glyphosate kills some of the beneficial bacteria found in a honey bee’s gut, making the bees more susceptible to infection. [Maybe we need to start feeding our bees some type of probiotic? I’m guessing.]
Glyphosate first came on the market in 1974. It provided an easy way to kill weeds with just a squirt. Glyphosate is used in agriculture and forestry, and to control aquatic plants. It is sprayed along railroad tracks, between orchard trees, and in public parks. According to the National Pesticide Information Center, there is a sodium salt form of glyphosate that is used to regulate plant growth and ripen fruit. So, it’s very useful and convenient. There are over 750 products on American shelves that contain glyphosate, including RoundUp, Bonide KleenUp Grass and Weed Killer, and Kleeraway Grass & Weed Killer. Tragically, glyphosate is also found in many oat products on grocery store shelves, according to the Environmental Working Group (EWG). The worst offenders the EWG listed include Giant Instant Oatmeal, Back to Nature Classic Granola, Quaker Dinosaur Eggs Oatmeal, and, I hate to say it, Cheerios. I urge you to read through their entire list and shop accordingly. The FDA was/is aware of glyphosate in our foods, but has failed to release its findings to the public. More recently, glyphosate has been linked to the development of Parkinson’s and Alzheimer’s diseases, and may also cause cancer in humans.
As with any herbicide, always follow the package directions EXACTLY and COMPLETELY. This is not a time to be careless. You can harm other plants with overspray, or you expose yourself to dangerous chemicals. This can occur by breathing it in during the application process, eating or smoking after applying it, if you don’t wash your hands, or by touching plants that are still wet from the spray. If exposure occurs, follow the first aid directions on the product label. For more information about risks and treatments, contact the Poison Control Center at 1-800-222-1222. Pets are also susceptible to herbicide poisoning.
Instead of using toxic chemicals to rid your garden and lawn of weeds, be industrious and put out the effort to pull them before they go to seed. While you’re out there, use it as a time to take a closer look at the other plants and the soil, and listen for the birds and insects that share your yard space.
Bottom line, glyphosate makes it possible to grow far more food, at least in the short term, but the long term costs, in my opinion, far outweigh any convenience or benefits it may provide.
The truth about nuts may surprise you.
While you probably already know that peanuts are not nuts (they’re legumes), many of the other foods you have come to know as nuts are not true nuts at all. Let’s begin by learning the botanical definition of nuts.
True nuts are hard-shelled, inedible pods that hold both the fruit and the seed of a plant. These pods do not open of their own accord, which means they are indehiscent. The pod, or shell, of a nut is made from the ovary wall, which hardens over time. Hazelnuts, chestnuts, and acorns are true nuts. So are kola nuts, which gives “cola” soft drinks their signature flavor.
[Did you know that small nuts are called ‘nutlets”? To me, that sounds like the perfect name for a little chihuahua.]
So, when is a nut not a nut?
A nut is not a nut when it is a fruit seed. Fruit seeds can be angiosperm, drupe, or gymnosperm seeds:
These not-nut nuts are commonly referred to as culinary nuts.
[Did you know that cashews are the seeds of an accessory fruit, which means they share characteristics with strawberries and poison ivy. Isn’t botany amazing?]
Of course, you can call any of these delicious morsels "nuts" whenever you want to. True nut or culinary nut, many of these yummy snacks find their way into our gardens and foodscapes. Which ones are you growing?
Did you know that soil has a wilting point?
It’s not that soil wilts, instead, wilting point is reached when the water needed by a plant to stay upright has been used up.
Water, plants, and soil perform an intricate dance. The soil has spaces, called macropores and micropores, that allow air, roots, and water to move through. The water molecules in the soil are strongly attracted to each other, using surface tension. This is how soil holds onto water, despite the pull of gravity. The amount of water a soil profile can hang onto is called its water holding capacity, or field capacity. When a soil is holding all the water it can, and becomes saturated, any additional water is pulled into the ground water by gravity, or runs off as urban drool, where it eventually is discharged into rivers, lakes, and oceans. At the opposite end of the soil moisture spectrum, a soil can be so dry that it becomes hydrophobic. Hydrophobic soil actively repels water.
Sponges act the same way. If you have a completely dry sponge, water will tend to run across the top, rather than be absorbed. Once a little water is absorbed, a lot more is pulled into the spaces that make up the majority of a sponge. Finally, if even more water is added, it will simply flow through the sponge.
Why the wilt?
Plants wilt for several different reasons. Bacteria or fungi may be blocking the xylem, there may be too much salt in the soil, ice damage may have occurred, or because the soil has reached the wilting point. When plants do not contain enough water, plant cells cannot remain plumped up, or turgid. As water becomes less available, cells shrink and become floppy. [Tree trunks do not get floppy because they contain lignin. Unlike cellulose, which is a sugar-based material, lignin is alcohol-based, but we will discuss lignin another day.] The problem with wilting is that there is a point of no return. This is a soil’s permanent wilting point.
Permanent wilting point
Permanent wilting point is death for plants. If a soil moisture rating reaches or surpasses the permanent wilting point, it doesn’t matter how much water you add later, the plant will die. This occurs more often with containerized plants, but it can happen anywhere.
Soil texture plays a big role in how much soil moisture is not enough to keep a plant alive. This is due to the soil’s ability to hold the water so tightly that plant roots cannot suck it in. The permanent wilting point occurs at 15 to 20% for clay soil, 10 to 15% in loamy soil, and at 5 to 10% in sandy soil.
You can monitor soil moisture using an inexpensive moisture meter.
If you hang a bird feeder in your yard, you are probably already growing millet.
Millet is those tiny, blonde seeds found in bird seed. It is also a delicious, easy to grow, gluten-free porridge. [In the same way as corn, rice, barley, and wheat, millet seeds are actually a specialized dry fruit, called a caryopsis, but we'll leave that for another discussion.]
Originally from Asia and Africa, people have been growing and eating millet for over 7,000 years. Some historians believe that millet played a major role in humanity’s shift from hunter-gatherers to farmers. Today, millet is still an important food source in many regions. You may be surprised to learn that millet, and not rice, is the primary carbohydrate food source in northern China. Millet can be eaten as a sweet, with milk and sugar, or as a savory dish, with the addition of meat and vegetables. Millet is high in protein, dietary fiber, and several B vitamins. A single serving of millet provides 76% of the RDA for manganese, which makes me wonder why we don’t eat more of it. The only cereal-related nutrient that millet is lacking is lysine, but buckwheat contains high levels of this important amino acid, so eating millet and buckwheat together makes for a healthy diet.
Types of millet
Millets are actually a group of plants in the grass family (Poaceae). Unlike most families, many millet varieties are only remotely related to one another. You can track down the different groupings, if you feel so inclined, but the most commonly grown are:
Sorghum, also found in bird seed mixes and cereal bowls, is sometimes called Great millet, but it is generally considered a separate cereal from millet.
How millet grows
Millet is an annual that grows quickly in hot, dry weather, on crappy soil. Of course, it performs far better when plant nutrients and irrigation are present, but it’s an extremely resilient plant. [The only thing it cannot tolerate is waterlogged soil and mud.] Depending on the variety, mature millet plants can reach a height of 2 to 5 feet.
Millet grows so fast that seeds will sometimes sprout while still attached to the spike! Normally, seeds germinate in 5 days, and spikes are ready to harvest in 50 to 180 days, depending on the variety and weather conditions. Because it grows so quickly, millet can also be used for erosion control, or as a green manure. It also tends to grow faster than most weeds. Millet is a good choice for filling in difficult spaces of the yard. Local birds will appreciate the free lunch, too!
How to grow millet
Millet seeds can be broadcast by hand over an area and raked in, or you can drill holes that are 1 to 4” deep for the seeds. [Did I mention that millet is rugged?] Once plants are established, they will readily self-seed the area, year after year. Because of millet’s high carbon to nitrogen (C:N) ratio, it is best balanced with low C:N plants, such as legumes, in crop rotation.
Millet pests and diseases
Generally speaking, millet has few pests, other than Bagrada bugs and crane flies. Millet diseases lean toward the fungal variety, with blast, leaf spot, downy mildews, ergot, rust, Johnson spot, smut, and blight causing the most problems. Simply provide good drainage and reasonable irrigation to avoid most of these diseases.
Millet, it’s not just for the birds (though you may need to protect your crop with netting or row covers, if you want any left to harvest). You can have it for breakfast, use it to increase biodiversity in your yard, or, if you’re feeling adventurous, millet can even be used to make alcoholic beverages!
Migration isn’t something people usually associate with gardening. But they should.
When we talk about migration, we generally mean large groups of animals moving from one region to another, due to seasonal changes, depleted food supplies, safety, and/or reproduction. Obviously, plants do not migrate in the proper sense of the word. [Wouldn’t it be a sight, if they could?]
To most people, migrations are left to caribou and wildebeests, whales and salmon, swallows and robins, and monarch butterflies. And therein lies our clue: insects migrate. And those insect migrations can have a huge impact on your garden.
Insects travel within a low, slow boundary layer, or significantly higher up, using fast-moving air currents. We are rarely aware of these massive migrations. Insects can sense polarized lights, and changes in wind speed and direction, helping them find their way. Insects also have built-in clocks that help them stay on schedule. The magnetic field theory related to bird and mammal migration appears to only impact short distance fliers.
Which insects migrate?
Several butterfly and moth, beetle, dragonfly, and African locust species migrate. [North American locust swarms do not occur seasonally, disqualifying them as migrations.] Even tiny aphids and lesion nematodes migrate, though their trips are significantly shorter.
In some cases, insect migrations work much like bat, bird, animal, and fish migrations: adults get a genetically-initiated urge to travel to a better wintering or breeding area. After spending a predetermined amount of time in the new location, the urge to return strikes, and off they go. In other cases, one generation will take the outgoing flight, and the next generation handles the return trip. In many cases of insect migration, it takes multiple generations to make the complete trip.
Between 33 million and a billion Monarch butterflies migrate each year, from Canada to Mexico and back again. Technically, since it takes four generations to complete the trip, these one-way excursions are called emigration, but we’ll ignore that detail. Monarch butterflies don’t harm our gardens, but other migrating insects can and will. And there are a lot of them.
According to the journal Science, over 3 trillion insects migrate over south-central England each year. England’s cold, damp weather makes it fair to assume that those numbers are profoundly higher in warmer areas.
The distances some of these insects travel is truly amazing. British painted ladies, or cosmopolitans, travel 9,000 miles over 6 generations. Wandering gliders, a type of dragonfly, travel 11,200 miles, with individuals flying 3,730 miles. For an insect that is only 1-3/4” long, it would be the same thing as a 6’ person traveling over 153,000 miles - under their own power.
Bay Area insects that migrate
Here, in the Bay Area, our gardens are impacted by several different migrating insects. These pests (and their favored foods) include:
You can join the citizen science movement related to insect migrations by reporting your sightings to The Big Bug Hunt. Your information will be added to countless other sightings to generate ever more reliable prediction models. This can help you protect your plants better, faster, and with less effort, using row covers.
Plants do not chow down on rocks like they were burgers and fries. Instead, their menu reads more like the Periodic Table. Plants absorb water from the soil. Minerals are in that water. Those minerals are plant food. Plants also produce their own food using the sun’s energy to create sugar.
There are 16 chemical elements critical to plant health. Depending on how much is needed, they are labeled as micronutrients (tiny amounts) or macronutrients (large amounts). Macronutrients are further divided between primary and secondary nutrients. Primary nutrients are the NPK of fertilizer bags. Plants use nitrogen, phosphorus, and potassium more than any other plant food, which is why they are the ones most often needing replacement. They are the rice and beans of a plant’s diet. Secondary nutrients, calcium, magnesium, and sulfur, rarely need to be supplemented, but they are very important to plant health. Micronutrients include boron, copper, iron, chloride, manganese, molybdenum, and zinc. [These used to be called trace elements.]
If you count up all those nutrients, you will only find 13. That is because plants also have non-mineral nutrients. These non-mineral nutrients are hydrogen, oxygen, and carbon. All of these nutrients work together to provide your plants with the energy and materials needed to grow. Some of those nutrients are mobile, while others are immobile.
Highly mobile nutrients go where they are needed within a plant. Nitrogen, potassium, phosphorus, magnesium, chloride, and molybdenum are all mobile plant nutrients. All the other nutrients are considered immobile because they stay where they were initially placed. Problems with mobile nutrients tend to appear in older leaves, while problems with immobile nutrients are seen in new growth. This is important to know because it can help you narrow down deficiencies and toxicities.
What is in your soil?
Before we take a closer look at each of these important factors to plant health, let me remind you that you cannot know what nutrients are in your soil without a soil test from a reputable lab. I wish those colorful plastic tubes from the store could do the job accurately, but they can’t. Not yet, anyway. Contact a local soil test lab and find out what you are working with. Not knowing the facts can lead to toxic levels of these nutrients, which can backfire. Just because your plants are not thriving does not mean they need to be fed. All too often, plant problems are caused by inhospitable soil conditions, unhealthy roots, irrigation problems, pests, or disease.
Also, different plants have different nutrient needs. Simply dumping a box of 10-10-10 around the garden isn’t a good idea and it’s a waste of money. Those chemicals can pollute groundwater and damage beneficial soil microorganisms. It can also make plants grow faster than they can maintain over the long haul, leaving them weak and vulnerable later in life. [For a hysterical read about the effects of too much fertilizer, check out Don Mitchell’s Moving/Living/Growing Up Country series.]
So, let’s see what each of these nutrients do for your plants:
Not enough of a plant nutrient, or too much, can cause problems. The tricky part comes in when the balance of nutrients is out of whack.
A man named Mulder created a chart that shows us the interactions between plant nutrients. Synergistic elements help each other to be absorbed by plants. Antagonistic elements get in each other’s way.
Using the chart above, you can see that proper levels of potassium help plants absorb iron and manganese, but too much potassium interferes with a plant’s ability to absorb boron, calcium, magnesium, nitrogen, and phosphorus. This interference can take the form of competition for space on water molecules, or it can alter soil pH, making some nutrients unavailable.
Plant food and soil pH
Soil pH ranges from 0 to 14, with lower numbers indicating acidity and higher numbers indicating alkalinity. Using the chart below, you can see that more nutrients are available, and there is greater microbe activity, when soil pH is between 6.0 and 7.0. Most plants can survive in soil pH from 5.2 to 7.8, but the narrower range allows plants to thrive. This is because the minerals use as food are ions. Ions are atoms and molecules that have a positive or negative charge. These cations and anions, respectively, attach themselves to water molecules and are pulled into the plant by root hairs. The wrong soil pH can cut your plants off from a bounty of nutrients.
Soil is given a cation exchange capacity rating to describe its ability to hold nutrients. [Did you know that root hairs knock cations (unbalanced atoms or molecules) loose with a hydrogen canon? Stay tuned for more on that!]
How to feed your plants
Personally, I prefer feeding my plants with composted yard and kitchen scraps and chicken bedding. Not only does this mix have excellent nutrients, it also improves soil structure. If you decide fertilizer really is necessary: READ THE BAG. Seriously. Federal law requires that important information is printed on the container and for good reason. Follow directions carefully and wash your hands when you’re done. Technically, there is no chemical difference between nitrogen from compost and nitrogen formulated in a lab. Nitrogen is nitrogen. The difference lies in everything else. What are the fillers? What else is in the compost that plants need? Honestly, there’s a lot we don’t yet understand about how living things interact. I prefer to err on the natural side, just in case.
Finally, keep in mind that a 10-pound bag of fertilizer does not contain 10-pounds of plant food. The numbers next to the letters tell you the percentage of total weight. This means that a 10-pound bag of 10-20-10 fertilizer contains 1 pound nitrogen, 2 pounds phosphorus, 1 pound potassium, and 6 pounds of filler. Yes, filler. If all your plants need is nitrogen, blood meal is a far better choice.
What are your plants hungry for?
Brown marmorated stink bugs have invaded the world!
Okay, so maybe that was a bit melodramatic, but the fact remains: brown marmorated stink bugs have exponentially increased their range and they can be serious garden pests.
The problem with stink bugs
Most stink bug species eat popular fruit and vegetable crops, such as apples, peas, peppers, as corn, raspberries, grapes, tomatoes, pecans, pears, peaches, nectarines, lima beans and other bean plants, blueberries, hazelnuts, and cucumbers. When they feed, stink bugs inject your garden plants with enzymes that break down plant tissue into juices they can suck up. This makes the fruit under the skin tough, and pretty unappealing to us. It also sets the stage for several bacterial, viral, and fungal diseases.
Stink bugs also feed on buds, flowers, leaves, stems, and new bark. Since stink bug populations can grow very quickly, they can cause significant damage. [They also like to overwinter in your home.] To make matters worse, insecticides do not generally work to control stink bug populations. So, what makes the brown marmorated stink bug an even bigger problem than other stink bugs?
The traveling brown marmorated stink bug
Brown marmorated stink bugs are originally from Eastern Asia. They are believed to have first appeared in the U.S., in Pennsylvania, some time between 1996 and 2001. These pests reached the West Coast in 2004, and are now found in over 40 states. While native stink bug populations tend to be controlled naturally by beneficial predators, such as parasitic wasps, this invasive pest has few natural enemies and, as stated earlier, it tends to be unfazed by chemical insecticides. This is why it is so important to be able to tell the difference between native stink bugs and brown marmorated stink bugs.
Brown marmorated stink bug identification
Adult brown marmorated stink bugs are 5/8 inch long and a mottled brown. Like other stink bugs, they have the telltale shield-shaped body. Some characteristics unique to these particular stink bugs include two white bands on the antennae, a blunt face, faint white bands on the legs, and a banded edge around the abdomen. If you are looking really closely (and why wouldn’t you?), you will also see that the thorax (shoulder area) is smooth, and there are dark bands on the tip of the membranous forewings. The folks at UC Davis made an informative video about the differences between brown marmorated stink bugs and more common, native consperse stink bugs.
Brown marmorated stink bug eggs are white to pale green, and barrel shaped. Eggs are normally laid in clusters on the underside of leaves, though I have also seen them laid in lines on bird netting. After hatching, nymphs go through fives developmental stages, or instars, in which they shed their skin, much the way a snake does, as it grows. Nymphs start out only 2.4 mm (less than 1/10 inch), and grow to reach 12 mm (just under 1/2 inch). Early nymphs are brown, with an orange abdomen. Second instars are nearly black, while later instars develop the characteristic mottled brown color. Initially, markings are red, then black, and finally white.
Managing brown marmorated stink bugs
Since insecticides don’t work, and there are few natural predators, what is a gardener to do about brown marmorated stink bugs? First, start by excluding them from your home and other buildings. Caulk openings, seal cracks, and use weatherstripping around air conditioners, doors, and windows. [This can reduce your electric bill, as well!] Next, since stink bugs are attracted to light, turn off unnecessary lights at night. [Another bonus for your utility bill.] In the case of heavy infestations, you can always use a shop vac or a handheld car vacuum to collect the little beasties. The most effective stink bug control is simply handpicking. You can drop stink bugs in a container of water with a couple of drops of dish soap, or feed the pests to your chickens.
Assassin bugs, green lacewing larvae, some parasitic wasps, and earwigs are also known to feed on stink bugs, so avoid using broad spectrum insecticides. Row covers can also be used to protect specific plants and crops against stink bug damage.
Brown marmorated stink bug lifecycle
Each autumn, these pests gather along fences, tree trunks, and buildings. From there, they move to a protected area where they overwinter in a resting stage called facultative diapause. In the spring, these adults become active again and start feeding. Within two weeks, they mate. Soon after, females begin laying the 200 to 500 eggs she will deposit in her lifetime. In the mid-Atlantic states, there are two generations each year. Here, in California, we do not yet know the extent of the brown marmorated stink bug’s reproductive capabilities. It is safe to assume that there will be even more generations here, where winters tend to be mild.
As temperatures begin to drop, many creatures search for winter shelter. That shelter may by your home, your gardening gloves, or, in some cases, a special sanctuary created by plants specifically for insects, spiders, and crustaceans. These tiny sanctuaries are called domatia.
The word domatium comes to us from the Latin word domus, meaning home. It’s the same root used for words such as domestic and domicile. Domatia are chambers created by plants specifically for bugs. When similar chambers are created as a response to damage caused by insects, fungi, bacteria, nematodes, and other plants, those chambers are called galls. The difference between galls and domatia is a little fuzzy, as scientists learn more, but we will stick with the classic differentiation for our purposes.
There is a range of structures that can be called domatia. Most often, domatia often found inside thorns and on the underside of leaves. While these spaces are really tiny, so are the insects they house. And what could provide better shelter than under a leaf or inside a pokey thorn? These minuscule shelters may be nothing more than a small divot, surrounded by plant tissue or hairs, or they may be large, bulbous growths, filled with channels and chambers.
Which insects live in domatia?
Some plants have evolved to create these tiny homes for certain insects, in a mutually beneficial relationship that may, or may not, benefit your garden. Ants and mites are the most common domatia residents. While these pests suck nutritious sap from our plants, carrying disease with them as they feed, they provide their hosts with nutritious poop and a certain measure of protection from potential invaders. Plants that house ants are called myrmecophytes [MER-meh-co-fights] and the homes they provide are called myrmecodomatia [MEER-ma-COD-o-ma-she-uh]. Sometimes, unwelcome guests move in. Thrips are one example.
So, grab a hand lens or a magnifying glass and take a closer look at all the amazing things going on in your garden!
Some soils can hold a lot of water and other soils can only hold a little water. Since many plant nutrients are held in suspension (in water), and nearly all plants need water to stay upright and alive, the amount of water a soil can hold has a huge impact on plant health.
The water holding capacity of a soil also has a big impact on how often you need to water and feed your plants. Nutrient loss, leaching, and water pollution are also part of the equation. Let’s find out what your soil’s water holding capacity is, and how it impacts your garden.
The first step to calculating your soil’s water holding capacity is to identify its texture. Soil texture refers to the percentage of sand, silt, and clay that makes up your soil. You may be surprised to learn that those words only refer to particle size, and not to any chemical properties. Very large particles (sand) have very large spaces, called macropores and micropores, between the particles, while clay particles have very tiny spaces.
These spaces allow air, water, nutrients, and roots to move through the soil. In the case of sand, the large macropores and micropores allow water to slip away quickly, carrying nutrients, pesticides, and other materials away with it. Loam, having smaller macropores and micropores than sand, slows the leaching of water, which increases that soil’s water holding capacity. Clay, with the tiniest macropores and micropores of all, has the highest water holding capacity, being able to hold up to six times the amount of water held by sand, but that ability comes at a price. Roots, air, and nutrients also have a difficult time moving through clay soil.
See the page on soil texture for a simple activity that will help you understand your soil’s makeup.
The way the soil particles clump together into aggregates is called soil structure. There are eight types of soil structure, based on size, shape, and stability. If you look closely at your soil with a hand lens or a simple microscope, you will be able to see these different shapes. The way the shapes create spaces within the soil impacts its water holding capacity. Soil structure also helps explain soil compaction. Some shapes and sizes, clay in particular, are far more likely to become compacted or have drainage issues
Water for plants
Not all the water held by a soil can be reached by plants. Sometimes it is too deep. In other cases, the water may be protected by a layer of rock. The amount of water in the soil that plants can reach and use is called plant available water. If a plant cannot reach enough soil water, it will hit a wilting point. At the opposite end of the moisture spectrum, field capacity (or drained upper limit) refers to the total amount of water a soil profile can hold. Anything beyond that amount leaches into groundwater, or runs off, as urban drool.
What is your soil’s water holding capacity?
You can conduct an experiment to see what your soil’s water holding capacity is, using simple household items. First, collect a soil sample from your garden. You may want to collect several different samples, for comparison. [Just be sure to label everything clearly!] Each sample should be the same size - 1/2 cup should work well. Then, place a paper coffee filter in a funnel, and put your sample in the coffee filter. Place the funnel into a large cup. Next, very, very slowly, pour 2 cups of water into the soil. Be sure to move the stream around, wetting all of the soil. Wait five minutes. Then, measure the water that flowed through the soil, into the cup. The difference between what you started with (2 cups) and what you ended up with will tell you how much water that amount of soil can hold.
Improving water holding capacity
Too much water and too little water are both bad for plants. Adding aged compost to your soil improves its water holding capacity, along with its structure, texture, and microbe biodiversity. As organic material decomposes, a wide variety of spaces, minerals, and plant nutrients become available, allowing roots to reach the food and water they need, without struggling in a pit of mud.
Soil texture determines how easy it is for plant roots to access the water and nutrients they need to survive and thrive. Soil texture also determines a soil’s ability to hold on to water and nutrients.
Soil texture is a measurement of the relative proportions of the sand, silt, and clay minerals found in a soil sample. Each of these words actually refers to the particle size of these soil separates, and not to any particular chemical property:
Sand particles can be seen with the naked eye. Silt particles can be seen with a standard, classroom microscope. To actually see clay particles, you would need to use an electron microscope, they are so small! Also, while most soil particles tend to be spherical, clay forms plates that generate up to 100,000 times more surface area. These means that there are many more potential points of attachment for nearby nutrients and water molecules.
Soil texture classifications
In the U.S., we use 12 different classifications to talk about soil texture. Each class has specific characteristics based on its feel, its tendency to crumble, and its likelihood of leaving a ‘stain’ behind on your fingers when handled:
You may also hear someone talk about soil that is fine textured or coarse textured. Finely textured soil contains more clay, while coarsely textured soil holds more sand. Soil texture is not the same thing as soil structure. Soil structure refers to the way minerals, air, water, microbes, and everything else is arranged into clumps, called aggregates.
Soil texture and drainage
The large and small spaces between these particles are called macropores and micropores, respectively. These spaces are what allow water, air, nutrients, and roots to move through the soil. In most cases, those spaces are similar in size to the particles they are around. Since water molecules tend to stick better to smaller particles, such as clay, and the micropores are smaller, clay has a far higher nutrient and water holding capacity than loam or sand. Clay is also more prone to drainage and compaction problems. Clay is also harder for roots (and shovels) to move through. The larger macropores and bigger particle size of sandy soils make leaching and nutrient loss more common problems. Erosion is another factor to consider when it comes to soil texture. Heavy sand and sticky clay are less likely to blow or wash away, while loam is more vulnerable to erosion.
Soil texture and nutrient retention
The nutrients used by plants are ions of specific elements. Ions are atoms or molecules that have either a positive or negative charge, due to the addition or loss of an electron. Cations, such as calcium and potassium, are positively charged and attracted to negatively charged soil particles. Anions, such as phosphorus and sulfur, are just the opposite. The ability of a soil to hold onto a positively charged mineral ion is known as its cation exchange capacity. Organic material and clay tend to have negative charges, while water and sand tend to be positively charged.
How to identify your soil’s texture
Use these steps to determine your soil’s texture:
For example, a 10” sample has 1” sand (10%), 7” silt (70%) and 2” (20%) clay:
Creating better soil texture
Ideally, your soil will be 50% macropores and micropores (containing 50% air and 50% water), 2 to 5% organic material (more is better), and 45 to 48% minerals. In a perfect growing medium, those minerals would be 40% sand, 40% silt, and 20% clay.
Rather than trying potentially disastrous quick fixes* to improve your soil’s texture, adding small amounts of organic material, such as aged compost, over a long period of time, will improve your soil’s ability to retain water and nutrients, while still allowing air, water, and roots the spaces they need to move freely.
* The most common quick fix for soil compaction, adding sand to clay, actually makes the problem worse, because the tiny clay particles fill the spaces between the sand particles. [Sand + clay = cement]
Plant prickles are skin spikes.
Unlike thorns, which are modified shoots, and spines, made from modified leaves, prickles are spiked skin extensions.
Because prickles are made out of epidermis and cortex tissue, they can occur anywhere on a plant. This is also what differentiates them from the hairs (trichomes) growing on your squash plant leaves. Trichomes only contain epidermis tissue, whereas prickles contain both epidermis and cortex.
The purpose of prickles
The most obvious purpose of prickles is to make plants less palatable to herbivores. Chewing on a stem covered with prickles can’t be very appealing. In extreme cases, such as the silk floss tree, the entire trunk is covered with massive prickles. I suppose that’s the level of protection needed in rural South America.
While prickles are generally meant to keep herbivores away, most species specific pollinators have learned to maneuver around the prickles without too much trouble. Prickles can also provide limited amounts of shade or insulation from temperature extremes.
A rose by any other pokey bit
Everyone calls the sharp bits on rose stems thorns, but they are actually prickles. One easy way to tell if a protuberance is a prickle, thorn, or spine, is by how easy it is to remove. Spines and thorns contain vascular bundles, but prickles do not.
This is why it is so easy to flick a rose thorn from its stem, while trying the same trick on your orange tree won’t work. Orange tree thorns have added strength from the phloem and xylem, carrying water and nutrients into the pointy protuberance. Thorns do not have that type of attachment, so they are easier to remove.
So, now you know the difference between thorns and prickles.
Predaceous ground beetles are a large family of beneficial insects that live in the soil.
You may see them scurrying across the ground, but mostly these members of Carabidae stay hidden in darkness. There are over 2,500 species of predaceous ground beetles in North America. They are mostly nocturnal and tend to hide under leaf litter and in the soil, though some species are attracted to lights at night.
Predaceous ground beetle description
Predaceous ground beetles are medium to large (1/3 to 2/3 inches long), shiny black or reddish beetles with long legs. Some species have brilliant coloration, and the shape can vary considerably. They have long, antenna with 11 segments and no knobs (clubs) at the end. The abdomen is large and rectangular, with a narrow thorax. While they can fly, they mostly prefer to run, which they do very quickly. Predaceous ground beetles look a lot like plant-eating darkling beetles. To tell them apart, you need to look closely enough to see if the second segment of the hind leg (trochanter), found between the coxa and femur, is enlarged. If it is, you have a predaceous ground beetle. Also, the antennae of predaceous ground beetles are attached just below a distinct ridge on the sides of the head.
Predaceous ground beetle life cycle
Eggs are laid in moist soil. When they hatch, larvae that look similar to earwigs emerge. These larvae feed voraciously on slugs and snails, and many bothersome soil dwelling insect larvae and pupa. These pest insects include masked chafers, caterpillars, grubs, tussock moth and gypsy moth larvae, other beetles, and maggots. These ground beetles will occasionally eat seeds and organic litter, but, as their name indicates, they prefer meat to vegetables. In fact, adult predaceous ground beetles can eat their body weight in food each day
So, the next time you see a black beetle running across the patio, look for fat legs and eyebrow ridges before squashing it!
Plants that are struggling need more fertilizer, right?
It makes sense. Your plants were doing fine, growing and thriving. Then, they started to decline. Leaves lost their color and fell off, stems lost their vigor, and flowers started looking like pale comparisons of their former selves. So, you add fertilizer and the plants look better. For a while. Then the decline returns. You add more fertilizer. And the cycle continues.
While you may think you are feeding your plants a healthy diet, what is more likely to be happening is toxic levels of some nutrients are building up in the soil, causing more complex problems. Excluding disease, insect attack, or improper soil pH, adding more fertilizer makes sense, on the surface. Except when it doesn’t, because sometimes that’s the last thing you should do. While there are certainly cases in which adding an all-purpose (hopefully organic) fertilizer is a good idea, more often than not, nutrient-based problems are more about imbalances and nutrient mobility.
Before we look at nutrient mobility, we need to understand a little bit about nutrient imbalances. In technical terms, this is called the cation exchange capacity. Put simply, cation exchange capacity (CEC) is a measurement of how many positively charged minerals can be held by the surface of a soil particle. Clay and organic material tends to be negatively charged, while many plant nutrients are positively charged. Mineral ions that are negatively charged are held in suspension, in water. These charged ions act like magnets. If the electrical charges are out of balance, plants cannot absorb the nutrients they need. This is why adding even more of an unnecessary nutrient can make matters worse, rather than better. In some cases, nutrients may already be inside your plant, but not where they are needed. This is where nutrient mobility comes in.
Plant nutrients and mobility
Plants absorb fourteen mineral nutrients from the soil. These nutrients are divided into macronutrients and micronutrients. Plants need large amounts of the macronutrients and small amounts of the micronutrients. Don’t be fooled, however. Just because a small amount is needed, doesn’t mean it is unimportant. As in the case of iron, insufficient levels can cripple a plant’s ability to absorb and use many other nutrients.
When a nutrient is considered mobile, it moves around inside a plant easily. Nitrogen is a highly mobile nutrient. Nitrogen deficiencies can be seen when nitrogen is pulled from older leaves, causing chlorosis (yellowing), to feed newer leaves. Other highly mobile plant nutrients include phosphorus, potassium, magnesium, chlorine, molybdenum, and nickel. When any of these nutrients become deficient, the symptoms will appear in older growth first.
Other nutrients are not easily moved once they are incorporated into a plant. In most cases, these nutrients stay where they are first dropped off, usually at growing points. This is great for as long as there is a steady supply of those nutrients. These immobile nutrients are difficult to move within a plant. It takes a lot of water to move them around inside a plant. This is why blossom end rot isn’t really caused by a simple calcium deficiency. Instead, it is caused by insufficient calcium and insufficient water, which is needed by the plant to move the calcium where it is needed when it is initially absorbed. Other immobile nutrients include sulfur, boron, copper, iron, manganese, and zinc. Deficiencies of immobile nutrients are more likely to appear in newer growth.
What nutrients are in your soil?
I’ve said it before and I’ll say it again: you don’t know what is in your soil without a soil test from a reputable, local lab. I wish I could say that those cute, over-the-counter soil tests were effective, but they aren’t. Not yet, anyway. Find a soil test lab on your side of the Rocky Mountains and send them a sample. That is the ONLY way to know what nutrients are available to your plants.
What are you feeding your plants?
Ajwain may be an unfamiliar word, but the ajwain plant carries an herbal punch that includes many more familiar spices and herbs.
Ajwain (Trachyspermum ammi) hails from India, North Africa, and the Middle East. Also known as ajowan, bishop’s weed, carom seeds, or ajowan caraway, ajwain is an umbellifer, along with carrots, dill, and celery. People have been eating ajwain leaves and fruit for a very long time, but many Americans are unfamiliar with this attractive edible.
If you were to look at a handful of ajwain fruit, you would swear they were seeds. Actually, they are schizocarps. Carrots, parsnips, cheeseweeds, and hibiscus all produce schizocarps. Schizocarps are tiny dried fruits that surround seeds.
Ajwain is an overachiever, when it comes to flavor. It is described as being similar to oregano and anise, with strong overtones of thyme. Apparently, these fruits are quite pungent - a little goes a long way. Because they are so strong, they are rarely used raw. In most cases, the schizocarps are dry-roasted or fried in clarified butter, before being added to curries or sprinkled over bread. The leaves are used in chutneys.
How to grow ajwain
In hot areas, ajwain is a perennial. Everywhere else, it is an annual. Ajwain can be grown from seeds or cuttings, with cuttings being the easiest method. To grow from seed, plant 1/4-inch deep in rich, potting soil, or scatter on top of the soil. Use a mister to water, to avoid washing all the seeds into a corner of the pot. Mist daily for a week or two, until germination occurs. Once the first true leaves emerge, you can transplant the seedling into a larger container. [I couldn't find any free images of ajwain plants, so you will have to wait until mine get started...]
To propagate ajwain from cuttings, take stems that are a few inches long and remove all but the upper two sets of leaves. Bury the stem in potting soil, with the leaves exposed ands water regularly. Before you know it, new roots will emerge.
Once your ajwain plant gets started, you will have to cut it back frequently, or it will take over an area. Any node that touches soil will develop new roots. Because of this behavior, ajwain is probably best grown in containers. The round, velvety, somewhat succulent leaves and fast growth make ajwain a candidate for a garden hedge, if you enjoy the fragrance. Because it is so pungent, most insects are not interested in ajwain plants.
If you happen to have a tummy ache, ajwain seeds can help relieve some of that discomfort.
Curly dock may sound like a fantastical marina attraction, but it’s actually an edible weed you probably already have growing nearby.
Curly dock (Rumex crispus) is also known as yellow dock or curled dock. There are several subspecies of curly dock, each adapted to distinct habitats. Curly dock is a perennial plant native to Western Asia and Europe. It is now found throughout the United States and Canada. Generally speaking, curly dock is considered an invasive weed. To make matters worse, curly dock is also a host plant of cutworms. Before you write off this sour salad green, keep in mind that it is also host to the ruddy copper butterfly, and it contains high levels of iron, vitamins A and C, and potassium.
Eating curly dock
Cousin to sorrel, and a member of the buckwheat family, curly dock leaves are larger and more bitter than its stylish relations. This bitterness is caused by oxalic acid. As such, only the young, tender leaves are harvested and eaten. You can also reduce the bitterness by boiling leaves in multiple changes of water, the same way some people cook collards. Mature leaves are generally too bitter to eat.
Curly dock description
Curly dock seedlings can be green or tinged with red. Wavy or curled leaves grow in a rosette, close to the ground, while flower stalks, or inflorescences, can reach 3 to 5 feet in height. Flowers are produced in clusters on these stalks. Fruits are triangular achenes, much like buckwheat. Curly dock seeds tend to catch on fur and sweaters, helping spread the species far and wide. Underground, curly dock features a large, forked yellow taproot.
If you’s rather get rid of the curly dock in your garden, limit wet areas. Curly dock loves moisture. Also, be sure to cut off and dispose of seed heads before they mature. Eventually, you will reduce the curly dock population in your garden.
If you happen to get stung by stinging nettles, rub a large curly dock leaf over the area to relieve some of the pain.
A person is called pithy when they are concise and forcefully expressive. Did you know that many plants can also by pithy?
Pith, also known as medulla, is a type of plant tissue that stores and transports nutrients. Typically, it is very soft and spongy.
In the very center of many stems, you can see a spongy area. This is particularly noticeable inside sunflower stems and their central cores, or steles. This is pith. Xylem surrounds the pith, and phloem are outside of the xylem. When pith first develops, it is white. As it ages, it can darken. In some plants, the pith may disintegrate completely, while, in others, the pith may have a chambered structure.
While the bitter white tissue found on the inside of a citrus rind is often called pith, that tissue is actually mesocarp, or albedo. The white membranes found inside pepper plants, however, really are pith.
If you happen to have a sago palm, the pith is highly toxic to animals when raw, but it is commonly used as a starchy food source in Micronesia. The toxins are removed and the starch is used much like tapioca.
Bacterial leaf scorch is a collection of diseases that can affect a wide variety of plants.
Bacterial leaf scorch (BLS), also known as bacterial leaf spot, is a tricky disease, because it is actually several diseases caused by different strains of a single pathogen. That pathogen, Xylella fastidiosa, causes different diseases in different plants. And sometimes those bacteria strains overlap their feeding habits, making classification and control difficult.
Leaf scorch diseases
Collectively, these diseases caused by Xylella fastidiosa are known as scorch diseases. Blueberries, mulberries, pears, peppers, plums, tomatoes, and even coffee plants can become infected with bacterial leaf scorch. Scorch diseases that go by a different name include:
Oak, sweetgum, oleander, sycamore, gingko, flowering dogwood, silk trees, jacaranda, maple, and elm can also become infected.
Lifecycle of Xylella fastidiosa
This particular bacterium is what’s called a fastidious mollicute, which means it must live within a plant’s xylem to be able to reproduce. The diseases they cause occur because they get so overcrowded that they block the flow of water and nutrients through the xylem.
Not all plants are negatively affected by this bacterium. Clover, blackberry, goldenrod, and many grasses can host this pathogen, acting as a way station without suffering any consequences. Unfortunately, when a sharpshooter feeds on one of these plants and then moves to your garden, trouble can start.
Symptoms of bacterial leaf scorch
Scorch diseases are characterized by the same symptoms you would see as a result of environmental conditions, such as herbicide overspray or too much fertilizer, or other diseases, such as verticillium wilt. Initially, you will see wilting and/or chlorosis. Leaf edges look, well, they look scorched! Then leaves start dropping. Fast. Before you know what happened, the plant dies. Except when it doesn’t, because sometimes it won’t. Scientists are still trying to sort it all out.
The bacteria that cause scorch diseases are carried into your garden by leafhoppers and spittlebugs. Actually, it’s in their saliva. Sharpshooters are the biggest carriers of the disease, as far as we know. These insect pests have a wide host range of their own. As sapsuckers, every bite they take infects the plant on which they are feeding. Because their host range is so large, they are spreading diseases to plants that have never been exposed before, so they have no defenses in place.
There are no known chemical treatments for scorch diseases, so controlling the disease carriers is your best bet. If the disease appears, remove the infected plant completely and put it in the trash.
Mulching and proper irrigation can help your plants protect themselves.
Curly top may sound like a cute little redheaded kid, but it’s really a viral disease of many garden plants.
Curly top host plants
This viral disease can strike beets, beans, ground cherries, peppers, pumpkins, chickpeas, tomatoes, squash, spinach, melons, horseradish, watermelon, and more. Scientists have identified different species of virus that cause similar symptoms. For lack of better ideas, those viruses are called Beet curly top geminivirus (BCTV), Beet mild curly top virus (BMCTV), and Beet severe curly top virus (BSCTV).
Symptoms of curly top
Infected plants exhibit leaves that cup upwards or downwards, depending on the plant variety. These leaves may turn a darker green than normal, or light green to yellow, and they are thicker and more brittle than normal. Puckering and wrinkling are also common. Infected tomato leaves may have veins that look purple.
The internodes (spaces between nodes on a stem) become shortened, causing stunting and dwarfing. These symptoms are more exaggerated when infection occurs while a plant is young, and death is common. Infected older plants often just turn yellow. The telltale symptom of curly top occurs when the top of the plant turns into a rosette or tiny bouquet. If any fruit is present, the skin will be dull, rather than shiny, it will taste bad, and will tend to ripen before it reaches full size.
Curly top virus lifecycle
The virus overwinters in annual and perennial weeds. From there, beet leafhoppers (Circulifer tenellus) carry the disease to your garden plants. Symptoms don’t start to appear until long after the leafhoppers are gone, but they are the disease vector, so controlling leafhoppers goes a long way toward preventing this disease. Unfortunately, insecticides are generally not effective against leafhoppers. Leafhoppers have many natural enemies, so make your garden hospitable to beneficial insects. You can do this by avoiding broad spectrum insecticides, planting a variety of umbellifers, such as dill, carrot, and fennel, and providing a water source.
The symptoms and host plants of curly top look too much like other viral diseases, such as spotted tomato wilt, to be identified by the casual gardener. Laboratory tests are needed to know for sure. In the case of viral disease, it is simpler to yank the plant and toss it in the trash, rather than spreading the infection to other plants.
Pulses are the grain seeds of plants in the legume family.
Legumes are a great high protein, high fiber food that tends to be pretty easy to grow. Popular legumes include beans, peas, lentils, chickpeas, cowpeas, and fava beans, just to name a few. Soybeans, carob, peanuts, tamarind, and alfalfa are also legumes, but not all legumes produce pulses.
Legume fruits, or pulses, are simple dry fruits that are low in fat. They develop from a single carpel and are normally dehiscent, which means they unzip along one edge. These fruits are often called pods, but that isn’t exactly inaccurate. Pulses are only one type of pod. A radish silique and a vanilla capsule are also pods. While peanuts and soybeans are both legumes, they both have a high fat content, they are not considered pulses.
No green pulses
If you harvest peas or beans while they are green, they are not called pulses. They are simply vegetable crops (even though they are fruits). The same is true for legumes harvested specifically for their oil. This is a rule put out by the United Nations’ Food and Agriculture Organization (FAO).
Differences between pulses and cereal grains
Cereal grains, such as rice, wheat, barley, corn, and sorghum certainly deserve garden space for their seed crops, they are not the same thing as pulses. Pulses may seem like just another bunch of seeds, but there are fundamental differences that make them stand alone:
The only true pulses are the seeds from dry beans, dry peas, chickpeas, and lentils. These plants provide one of the best bangs for your gardening buck, providing excellent nutrition and soil health improvement.
Escarole is a ‘bitter green’ member of the chicory family that looks like a lettuce, but packs a powerful nutritional punch. And no Italian wedding soup would be right without it.
Escarole has been eaten and cultivated since Egyptian times. Escarole is an excellent addition to soups and salads, providing both flavor and texture. It can also be baked into casseroles, sautéed, added to pasta, or used to wrap meat or fish. [Lightly sautéing or braising escarole is the best way to bring out its sweetness.] In fact, it is easier to find recipes for escarole than growing tips. But grow it we shall!
The escarole plant
Cousin to radicchio, escarole is a subspecies of endive [on-deev]. The endive species is divided between curly endive or frisée (var crispum), with narrow, toothed leaves, and escarole, or broadleaf endive (var latifolia). Being a type of chicory, escarole has darker outer leaves and pale green to white inner leaves. The degree of greenness to a leaf is an indicator of its bitterness. The chemicals that create the bitterness are said to aid digestion. This group of plants also produces a milky white latex than can cause skin irritation for some.
Escarole, and other chicories, are biennial plants grown as annuals. If you allow them to go through their full lifecycle, as I do, the flowers will attract pollinators and you will find escarole turning up everywhere that it can grow!
How to grow escarole
In hot regions, escarole seeds are generally planted in early fall through early spring, successively. This helps avoid bolting, or going to seed, before plants reach full size, and ensures a ready supply of fresh escarole for the kitchen. While they are less likely to bolt than lettuce or spinach, escarole leaves do not taste very good once this process begins.
Escarole is grown much like lettuce, in that it prefers full sun, consistent moisture, temperatures between 50 and 75°F, and a soil pH of 6.0 to 6.8, ideally. Like lettuce, if the soil dries out too much, growth will slow and the leaves will become too bitter to enjoy. Prepare the seed bed by top dressing with aged compost.
Seeds are planted 1/4-inch deep and thinned to 6 to 12 inches apart. Plants growing too close together are more likely to bolt. Side dressing with more aged compost will provide valuable nutrients, retain moisture, and slow weed growth. Escarole also makes a lovely container plant, indoors or out. Escarole matures in 85 to 98 days, depending on conditions.
Escarole pests and diseases
Aphids, flea beetles, beet leafminers, cabbageworms, cabbage loopers, leafhoppers, slugs and snails, and cutworms may feed on your escarole plants, but they rarely cause serious damage. You can use brassica collars to protect young escarole from cutworm damage, and row covers to block many of the other pests. Diseases of escarole include damping off disease, downy mildews, Alternaria leaf spot, Rhizoctonia blight, white mold, leaf rot, and bottom rot.
You can remove outer leaves any time you like, or cut the entire plant off at ground level. Leaving the root system in place feeds the soil microorganisms that help our plants thrive.
Escarole does not freeze well, but many of the recipes that use escarole do, so cook it up and freeze it for later use.
You can grow a surprising amount of food in your own yard. Ask me how!