By planting year-round, you are providing for the soil microorganisms that help your plants grow. You will also be providing your family with fresh, healthful food without ever leaving your yard.

Without sunlight, most plants can’t grow.

Plant labels may tell you how much sun exposure a plant needs, but the terms can be confusing. You’ve seen the words, but what do partial sun and partial shade mean? Are they the same thing?  No. Let's find out why.

Full Sun

Full sun means 6 to 8 hours of direct sunlight every day. Full sun is usually found on the south side of your house (assuming you live in the northern hemisphere). Plants that thrive in full sun are your go-getters. Most summer crops prefer full sun. Artichokes, fruit and nut trees, herbs, melon and tomato family members need 8 to 10 hours of direct sunlight during the growing season. Plants with silver or gray foliage also prefer full sun.

Partial Sun

Partial sun means 3 to 6 hours of sunlight in the afternoon, usually found on the west side of your house. We can call these the late sleepers of the plant world. They need time to wake up and may not be ready to deal with sunlight until later. Alliums, blackberries, peas, and root crops can be grown in partial sun.

Partial Shade

Partial shade means 3 to 6 hours of morning sun with protection from more intense midday and afternoon sun. These are your early risers. Leafy greens, raspberries, and Swiss chard grow well in partial shade.

How much sun does your yard get?

Knowing how much sunlight an area gets can help you select the right plants for that space. Before planting, create a sun map of your yard. A sun map will tell you how much sunlight each area gets. And remember, those areas change with the seasons.

Plants can create shade for other plants, too. For example, you can grow chives under artichoke plants. This companion planting or intercropping takes advantage of the shade produced by larger perennials to protect less sun-tolerant plants.

If you garden using traditional rows, your plants will get the most sun exposure if those rows run north to south and your tallest plants are at the northern end of your garden plot.​

Thrive or survive?

We’ve all seen examples of tenacious, wind-battered trees growing impossibly out of rocks, but we want life for our garden plants to be better than that, don't we? We don’t want our plants to simply survive, we want them to thrive! This is where rooting depth becomes so important. Plants will make do with whatever they have available to them. By providing enough loose, healthy soil, our plants will be more productive and less likely to get sick.

How deep plant roots go depends on several variables: species, soil structure, soil health, soil moisture levels, and probably a thousand other things. Roots will go where they need to to find water and nutrients. Imagine carefully digging up specimens of your garden plants to see what their root systems really look like. Ends up, it’s already been done. Back in 1927, a couple of researchers, Weaver and Bruner, dug up a bunch of vegetable plants to examine rooting depth and structure. We can use what they learned to make sure we put our plants where they will grow best.

​And that lawn, its root system is pitiful compared to native plants.

Slightly deeper growing plants, arugula, bok choy, celery, fennel, garlic, Jerusalem artichokes, mint, onions, rosemary, shallots, strawberries, and Swiss chard need at least 12” of soil but perform better in 18” or more soil.

Moderately deep rooted plants

Your cabbage, carrots, chiles, okra, peas, beans, beets, blueberries, broccoli,  collards, Brussels sprouts, cauliflower, cucumbers, eggplant, horseradish, kale, leeks, kohlrabi, mustard greens, Napa cabbage, peppers, potatoes, rutabagas, sweet potatoes, and turnips need at least 18" of soil to grow properly.

Rooting depth depends on species, soil, and several other variables. Knowing more about rooting depth can help you select plants suited to your soil, container size, or planting beds.

Blackberries and raspberries, cherries, citrus, cucumbers, eggplants, grapes, melons, peppers, pineapples, pomegranates, pumpkins, squashes, strawberries, and watermelons are not climacteric and must be left where they are until they have ripened fully. If these fruits are harvested before they are ripe, put them in the compost pile or feed them to your chickens because they will never ripen. There are some non-climacteric apricots and melons, while some varieties of grapes and strawberries, while not climacteric, do have active ethylene gas receptors.

Suckers, also known as basal shoots, and root sprouts can be removed from mature plants and encouraged to take root elsewhere. To do this, you will need to carefully remove them from the parent plant and place them in moist soil. ​

What about GMOs?

Propagation generally refers to breeding or reproducing plants by natural processes from parent stock. How you define natural processes may alter how you feel about genetic modification. Before digging in your heels, you need to know that plants, bacteria, and fungi have been modifying genetic material [their own and that of other living things] long before we got started in the lab. For better or worse, genetic modification has a role in modern plant propagation. For one thing, without genetic modification, there would be no seedless watermelons. Seedless watermelons happen because plant breeders do two things:

1. They take the normal 22 watermelon chromosomes and double them, using a chemical process.
2. They pollinate female flowers of plants with 44 chromosomes with male plants that have 22 chromosome.

The resulting offspring have 33 chromosome and are highly unlikely to have viable seeds. That’s why you still get an occasional seed in your seedless watermelon.

Rather than going to the store to buy new plants, you can often propagate your own for free using these methods.

The world’s largest life form

Tree roots spread. Then they can send up new root sprouts, which then create more roots and more root shoots. Given enough time and space, this process can create something really HUGE! In fact, root shoots are responsible for one of the world’s largest and probably oldest life forms: the singular root system of a grove of male quaking aspen found in Utah. Known as Pando, this root system covers 106 acres, weighs approximately 13 million tons, and is believed to be 80,000 years old. Sadly, Pando, is dying. Pando’s decline is believed to be a combined result of drought, grazing, and fire suppression. The U.S. Forest Service and private groups are trying to save it, but repeatedly killing off the root shoots with grazing (or hand pruners) does take its toll.

Why do trees produce root sprouts?

Some trees are more likely than others to produce root sprouts. In some cases, it is simply the tree’s normal method of propagation. Root sprouts can also be a sign that a tree or shrub is stressed. That stress can take many forms:

• too much or too little irrigation, nutrients, or sunlight
• wrong planting depth
• frequent heavy wind
• borer infestations
• restricted space due to buildings, etc.
• too close to a heat sink

What can you do about root sprouts?
First, keep your tree as healthy as possible. Water it, feed it, protect it from lawn competition, weedwackers, and car doors. Mulch around but not touching the tree. Do a little research to find out what type of tree you are dealing with and what its needs are, and provide for those needs. This will reduce the tree’s drive to reproduce in this way.

If you spray herbicides on a root sprout, you will be poisoning the parent plant as well. Instead, you can kill the individual buds by tearing the new growth off, as close to the root as possible. Of course, this may require some soil removal. If you can tear the root sprout off of the root, you are likely to damage or kill that particular bud. If there is a section of root that continually puts out unwanted root sprouts, you can dig up the offending root and severe it from the tree or shrub. If all of that sounds like more work than it is worth, simply snip them off at soil level each time you see them.

There are also products available that you can spray on root sprouts, but I do not use them. Reviews appear to be highly mixed and applying just a little bit too much can seriously damage the tree or shrub those root sprouts came from. Other people swear by them. It's your call.

If you are really sick of all the root sprouts in your lawn, contact a licensed arborist. They can safely apply a growth inhibitor.

Carbon cycle components

Carbon can be found everywhere on, in, and around the Earth. The way carbon moves from place to place, and from form to form, is what makes up the carbon cycle. The components of the carbon cycle are:

• atmosphere - carbon dioxide and methane both absorb and retain heat; carbon can dissolve in raindrops that fall to the Earth in an acidic form [carbonic acid]
• biosphere - all living things, dead things, and soil
• oceans - including living and non-living marine life and dissolved inorganic carbon
• geosphere - sediments, fossil fuels, fresh water systems, and the non-living organic material they contain
• Earth’s mantle and crust

Carbon moves through these changes because of biological, chemical, geological, and physical processes.

The carbon cycle in your garden

The same processes occur in your garden, with similar results. Start with your soil. Soil is a living, breathing complex of minerals, organic matter, insects, microorganisms, worms, and more. Microorganisms break down complex molecules into smaller bits, separating carbon from whatever it happens to be bound to and making it and other minerals available to plant roots as food.

You plant a seed and water it. The seed coat softens, a first root, or radicle, emerges and starts absorbing carbon and other minerals. The carbon then becomes part of the plant. The plant matures and produces fruit or other edible parts, which we harvest and eat. The carbon in those parts then becomes part of us. The parts we don’t eat are added to the compost pile, where the carbon attaches itself to other minerals or is released into the atmosphere as carbon dioxide. 

The sun shines down on Earth’s oceans, waterways, and soil causing evaporation. That moisture condenses and rain occurs, converting any carbon dioxide in the atmosphere into carbonic acid. This form of carbon falls to Earth, enters the soil, and hydrates any unharvested plants. Excess rainwater leaches into ground water where it ultimately makes its way to oceans. The sun’s heat causes more evaporation, water rises into the atmosphere, more rain, and so on.

How do plants use carbon?
​
You may have heard that plants take carbon dioxide in and release oxygen during the day, and that that process switches at night. The truth is, carbon dioxide is only taken in, and oxygen is only released back into the environment, while photosynthesis is actively taking place. The act of photosynthesis spilts the carbon dioxide molecule into oxygen and carbon. The carbon is used as a building material, much the way our bodies use carbohydrates. [Carbohydrates are made out of carbon, hydrogen, and oxygen.]

Plants also absorb carbon from the soil, but there has to be the right balance of nitrogen available for plants to use the carbon they need. Nitrogen is the steak and salad equivalent of the human diet. This balance is called the carbon-to-nitrogen, or C:N, ratio. Microorganisms that break down minerals and organic matter into plant-sized bites prefer a C:N ratio of 24:1 to 30:1. If there is too much, or not enough, carbon or nitrogen in the soil, plants will suffer.

Carbon cycling and tap water

Most soils contain a variety of carbon compounds and this can be a problem if your tap/irrigation water is highly alkaline. The chemical reactions that occur between carbonate and bicarbonate ions and alkaline water can make calcium and magnesium less soluble, and harder for plants to absorb. These chemical transformation between these molecules also tends to leave salts behind. Whenever possible, irrigate your garden with rain water.

Carbon sequestering

As we burn fossil fuels and seal the Earth’s surface with concrete, we release an awful lot of carbon into the atmosphere and make it harder for carbon to be absorbed into the soil. Carbon in the atmosphere joins with oxygen to form carbon dioxide. Carbon dioxide (and methane) absorb heat and bounce it back to Earth. This can help prevent another Ice Age and it can lead to global warming, more destructive storms, desertification, rising sea levels, and a harder time for us and our plants. 

Removing carbon from the atmosphere is called carbon sequestering. Naturally, carbon is held in plants and soil. When plants are composted or decompose, some of the carbon they contain is returned to the atmosphere and some enters the biosphere, oceans, and geosphere. 

As we disturb the Earth’s surface, we break the bonds that hold carbon in place. Instead of plowing or rototilling, you can reduce the amount of carbon released into the atmosphere by practicing no-dig gardening. [It’s easier on your back, too.]

Carbon is sequestered into the soil by plant roots. Plant roots secrete carbon in something called exudates. Root exudates feed beneficial bacteria and fungi in the soil which then help feed your plants. These root exudates also promote soil health and reduce erosion.

There are many ways that you can reduce the amount of carbon in the atmosphere:

• protect soil with mulch or cover crops
• plant perennial crops, such as artichoke, rhubarb, and fruit and nut trees
• compost plant debris and kitchen waste properly
• install a rain garden
• use native plants and those suitable to your microclimate
• get a lab-based soil test before adding unnecessary fertilizers
• avoid using potting soil that contains peat
• irrigate your garden with rainwater collected in rain barrels or other means
• buy used items whenever possible, rather than new, and only buy what you actually need
• avoid heating the outdoors with fire pits, BBQs, and patio heaters
• never burn trash, build bonfires, or make biochar
• plant large trees near your home to reduce the need for A/C
• if you have a lawn, allow it to get taller before mowing

Finally, growing your own food is one of the easiest ways to reduce the amount of carbon released into the atmosphere. Not only does it reduce the demand for highly tilled fields around the globe, it reduces the number of trucks, ships, farming machinery, and storage facilities needed to fill your larder. Just go outside and pick what you need!

Winter is when many fruit and nut trees and cane fruits enter dormancy. This is an excellent time to prune and train trees and canes. It is also a good time to apply anti-pest and anti-disease treatments. But some of those treatments should be applied when a plant is in full dormancy while others should be applied during the delayed dormant period. Let’s find out more about these two time frames and how to make the most of them.

​Life in the year of a tree

Summer is a riot of leaf, flower, and fruit development. Ample warmth and moisture combine to allow trees and canes to invest all their resources into procreation. As days begin to shorten and temperatures start to drop, deciduous trees, grape vines, and bramble fruits pull resources from leaves, as seen by the changing colors and ultimate leaf drop. During the coldest part of winter [December and January if you live in San Jose, California], most fruit and nut trees are in full dormancy. Sometime around February, things start moving again. Sap starts flowing. Buds start swelling. This is called the delayed-dormant period and it continues until spring, when the tips of the buds start to turn green.

Timing tree treatments

Horticultural oils, fixed copper, Bordeaux mixture and fungicides can be used to suffocate pest eggs, thwart fungal diseases, and break many other disease triangles. But the timing of those treatments is critical for them to work properly. Spray too soon and rain will wash it away before it ever comes into contact with a pest or pathogen. Too late is, well, too late. Also, coverage must be complete to the point of it dripping from every surface.

Generally speaking, these treatments need to be done before buds start to swell. Applying horticultural oils during summer, for example, when trees are more likely to be water-stressed, can lead to severe leaf loss and sunburn damage, reducing crop size and making trees susceptible a number of other pests and diseases. Applying treatments during freezing weather can be just as bad. Ideally, tree treatments should be applied on cool (50°F - 70°F), slightly overcast days, when rain, fog, and wind are not expected for at least 24 hours.

Different species have different ideal “windows” of treatment opportunities:

• Apple - green tip stage
• Apricot - up to first bloom
• Avocado - does not enter winter dormancy and should not be given winter treatments
• Cherry - white bud
• Citrus - does not enter winter dormancy and should not be given winter treatments
• Peach/nectarine - pre-bloom
• Pear - cluster bud
• Walnut - should never be treated with oils in winter

Timing also depends on the specific pest or disease. Full dormancy is the best time to treat for San Jose scale and peach leaf curl. Either full dormancy or the delayed dormant period can be used to treat for aphid eggs, European fruit lecanium nymphs, fruittree leafrollers, peach silver mites, and peach twig borer larvae. You can also wait until blossoms appear to use Bt to treat for peach twig borers.

The delayed dormant period is the best time to apply treatments for these specific problems:

• Anthracnose (blackberry, grape and raspberry)
• Black rot (grape)
• Brown mite eggs
• Cane blight (blackberry and raspberry)
• Downy mildews (grape)
• European red mite eggs
• Fireblight
• Leaf spot (grape)
• Mummy berry (blueberry)
• Obliquebanded leafroller larvae
• Pear psylla eggs
• Phomopsis cane and twig blight (blueberry and grape)
• Septoria leaf spot (blackberry and raspberry)
• Shothole fungus
• Spur blight (raspberry)
• Twig blight (blueberry)
• Yellow rust (raspberry)

Overlapping treatments

In some cases, your tree, vine, or canes will need more than one type of treatment. Dormant oil may be needed to combat certain pests, followed by a sulfur treatment to prevent fungal disease. It is very important that at least 30 days separate those two treatments. Also, sulfur should not be applied on days when temperatures will go above 75°F.

Keep in mind that treatments should not be given as a matter of habit. They should only be used when they are needed, as evidenced by infestations of infectious the previous year. Use a hand lens or magnifying glass to inspect buds for signs of aphid or other insect eggs. If your trees do not need treating, don’t do it. This is especially true for fixed copper treatments, as copper can build up in the soil to reach levels that are toxic to valuable microorganisms.

​Whichever treatments you decide to use, ALWAYS apply them exactly as package instructions state and wear protective clothing and goggles. Using these products incorrectly can harm you, your trees, and groundwater supplies.

Other actions you can take to ensure the health of your fruit and nut trees during delayed dormancy include:

• Remove mummies to interrupt navel orangeworm and brown rot.
• Remove deadwood and twigs with cankers and lesions.
• Remove fallen leaves which may contain pest eggs or disease pathogens.
• Whitewash trunks and exposed branches to reduce frost and sun damage.

February may seem like a quiet time for gardeners, but it is the perfect time to get outside and take a closer look at stems, twigs, bark, buds and spurs. Identifying potential pest and disease problems ahead of time, and treating your trees at the ideal time to combat those problems can make the rest of your year that much easier and your trees more productive.

When installing new bare root trees, or doing dormant season pruning, look for orange bulges on stems or branches. It might be burr knots.

Once considered a disease, burr knots start as smooth orange bulges on stems or branches that develop into adventitious roots. These tumor-like bulges are masses of tiny roots that somehow ended up in the aboveground portion of a tree. This condition can be mistaken for crown gall.

Grafted trees

Remember, most fruit and nut trees purchased these days are two trees grafted together. The upper portions produce more fruit and have good pest and disease resistance. Rootstocks establish themselves quickly and make the best use of soil resources.

Trees susceptible to burr knots

This condition is most common in apple trees. It occurs on scion cultivars, particularly 'Gala' and 'Empire', and dwarf and semi-dwarf tree rootstocks. Specifically, semi-dwarf trees grown from M.7, M.26, MM106, or MM.111 and dwarf trees with M.9 rootstock are likely to develop burr knots. Scion cultivars tend to develop burr knots on the underside of limbs, while grafted trees develop burr knots at nodes. Nodes are where  leaves and stems emerge. Instead of developing normally, these primordial root cells grow, creating a tumor-like bulge.

Conditions that encourage burr knots

Too much shade can increase the likelihood of burr knots occurring. High humidity and temperatures ranging from 68°F to 95°F during the first year also encourage the development of tiny growths, called root initials, during its second year. These root initials can break through the bark of a tree, making room for more roots to form, increasing the bulge.

Problems associated with burr knots

As roots push through the bark, they create entry points for pests, such as plum borers, apple clearwing moths, wooly apple aphids, and diseases. These diseases include fireblight and wood-rotting fungi. Limbs can become structurally weak and more likely to break. Several burr knots on the same tree can also interfere with the nutrient movement through the phloem, causing stunting. These weakened areas are more prone to frost damage winter.

Preventing burr knots

These tips can help your tree stay healthy and free of burr knots:

• Select tree varieties that are suitable for your microclimate. 
• Install trees at the proper depth. 
• Keep weeds away.
• Use tree supports properly and only for as long as needed. 
• Cut out any burr knots seen.

Angio- or gymno-?

There are several differences between angiosperm and gymnosperm:

• Angiosperms, or flowering plants, produce flowers and fruits, whereas gymnosperms do not.
• Angiosperms have a trachea-like structure in the xylem, called a vessel element. Gymnosperms do not have that structure. 
• Angiosperms and gymnosperm are both vascular plants. They have xylem, which are used to help water rise up into the plant from the roots. They have phloem which allow sugar produced via photosynthesis to flow down throughout the plant. The walls of a gymnosperm’s phloem, however, is riddled with holes. This sieve element allows nutrients to move to neighboring cells.

Another difference between angiosperm and gymnosperm is the idea of softwood versus hardwood. Those terms don’t exclusively refer to the density of the wood. It actually points out that they are two entirely different types of plants. Hardwoods are angiosperms, while softwoods are gymnosperms.

Types of gymnosperm

Gymnosperm seeds, unlike angiosperm, develop on top of leaves or scales. Those scales often turn into cones. There are four existing types of gymnosperm:

• conifers - cypresses and pines
• cycads - Sago palm
• Ginkgo
• gnetophytes

Nutty gymnosperms

You may have heard of pine nuts and gingko nuts, but neither one is actually a nut. True nuts are hard-shelled, inedible pods that hold both the fruit and the seed of a plant. 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.

A nut is not a nut when it is a fruit seed. Pine nuts and ginkgo nuts are not true nuts.

While most of the plants in your garden are probably angiosperms, you just might have a gymnosperm or two in the mix!

Fern reproduction

Ferns are unique in their method of reproduction and they are the only plants with two distinct living stages. As each spore matures, it becomes a sporophyte. Sporophytes that land in hospitable environments grow into very tiny, short-lived plants called gametophytes. Gametophytes have two sets of reproductive organs: a female archegonia and a male antheridia. Fertilization can take place within the same plant or between two neighboring plants. This fertilization produces a new sporophyte that grows into an adult fern.

Edible ferns

While most ferns are not considered edible, they also tend to not be poisonous. There are some varieties of fern that are edible, such as:

• bracken (Pteridium aquilinum)
• cinnamon fern (Osmundastrum cinnamomeum)
• king fern (Ptisana salicina)
• licorice fern (Polypodium glycyrrhiza)
• ostrich fern (Matteuccia struthiopteris)
• royal fern (Osmunda regalis)
• vegetable fern (Diplazium esculentum)

As always, do not eat anything you are not sure to be safe.

Fern pests and diseases

Ferns are naturally resistant to most plant-eating insects. One edible fern in particular, Tectaria macrodonta, has a gene that was transferred to cotton plants, providing resistance against whiteflies! Foliar nematodes (Aphelenchoides fragariae) and soil borne nematodes (Pratylenchus) can sometimes be a problem.

Ferns are susceptible to diseases such as bacterial blight (Pseudomonas cichorii or P. gladioli), Pythium root rot, and Rhizoctonia blight. Infected plants should be discarded. Environmental problems, such as drought, which causes graying, and over-fertilization, which results in frond lobing and leaf tip burn, can be avoided with good cultural practices. This means investing in disease-free plants, using only as much fertilizer as recommended for each fern species, and avoiding overhead watering. 

If you have a moist, shady crevice in your garden, ferns might be just what you've been looking for!

Types of tropism

​Tropisms can be positive or negative. Positive tropisms attract the plant toward the trigger, while negative tropisms push the plant away. Sunlight is generally a positive tropism, causing plants to lean, turn, and pivot to follow its rays. In some cases, particularly darkened jungle floors, sunlight is a negative tropism, initially, driving vines to seek trees which they will later climb. ​

Tropisms are generally named for the stimuli:

• gravitropism - roots grow downward (positive tropism) and stems grow upward (negative tropism) in response to gravity; also known as geotropism
• heliotropism - pivoting movement that allows plants to follow the sun’s movement across the sky
• hydrotropism - the root cap senses water in the soil and grows toward it
• phototropism - stems grow upward, toward sunlight
• skototropism - vines move away from sunlight in order to find trees to climb
• thigmotropism - tendrils twine around supports

Plants also respond to chemicals (chemotropism), electric fields (electrotropism), magnetic fields (magnetotropism), oxygen levels (aerotropism), and temperatures (thermotropism)

The opposite of tropism

When a plant responds in a direction that is not determined by the position of the stimulus, it is called a nastic movement. Common nastic movement triggers include being touched or the way a flower opens and closes each day (nyctinasty). When being touched causes flowers or leaves to suddenly close themselves up in a specific and regular pattern, rather than the thigmotropism seen in climbing tendrils, it is a nastic movement. The location of the finger has nothing to do with the way the flower closes. In the latter case, the sun going down may trigger the flower to close, but the direction of that closing is not related to the sun’s position.

Plants may not be able to get up and walk around, but they have a unique arsenal of movement-related responses they can use to help themselves grow and thrive.

Which tropisms do you see in your garden?

Cavitation is the sound of water breaking. 

While we don’t normally think of water being able to “break”, the columns of water that move upward through a tree’s veins can be broken, allowing air bubbles to form or simply severing a pathway for life-giving water.

Trees use a lot of water

The general rule of thumb for how much water a tree needs each week of summer is 10 gallons of water for every inch of trunk diameter, as measured at knee height. This means a large, mature tree, with a trunk diameter of 18”, will need 180 gallons of water every week at the peak of summer, on average. The flow of that water is critical to a tree’s health.

Transpiration

In healthy trees, water is absorbed through the roots and pulled upward through tubes called xylem. There are thousands of xylem in a mature tree. Picture the xylem as straws that run the vertical length of a tree. Water moves through xylem in a process called transpiration. 

Transpiration refers to the way negative pressure is created within xylem as water evaporates from the surface of the leaves. This occurs because of surface tension, or the tendency of water molecules to stick together. When one water molecule leaves the plant through evaporation, lower water molecules are pulled upward.

Bubbles can be bad

Bubbles might be fun to play with, but bubbles in veins are bad. Just as air bubbles in an IV tube can kill you, so, too, can bubbles block the flow of life-giving water for a tree. Rapid transpiration can cause air bubbles to form in xylem. If too many air bubbles remain in place, it can kill a tree. Cavitation is much like an embolism for trees. Small, infrequent bubbles are not a serious problem. Large, fixed bubbles are deadly.

During periods of drought, the rate of evaporation on the surface of the leaves is so great that xylem can collapse and break, like a rope pulled too tautly. These breaks halt the flow of water completely, also killing a tree. Cavitation also occurs in response to thawing after water within a tree has frozen.

The sound of silence
If you could hear higher frequencies, it would sound similar to popcorn popping. In most cases, the frequency of this sound is too high for us to hear, but it can, occasionally, be heard. [It might be fun to try using a stethoscope on a tree…] I can only imagine that our peaceful summer walks in the woods sound more like a riot of trees screaming for water to our dogs…

​Bottom line: make sure you irrigate your trees properly to keep them healthy, especially during summer.

Juicy, sweet kernels of corn transform, overnight, into hideous, purple-gray, tumors. And these tumorous galls are delicious! 

Introducing, corn smut.

Now, corn has many pests and diseases: corn earworms, European corn borers, seed-corn maggots, soft rot, seed rot, fusarium root and ear rot, maize dwarf mosaic, pythium stalk rot, and damping off disease, just to name a few. If you are an American corn farmer, corn smut is not what you want to see in your field. A lot of money and effort have gone into eradicating corn smut in North America. 

Corn smut in your garden is something else entirely.

While this distant cousin of mushrooms reduces crop size and makes ears of corn unmarketable for July picnics and canning purposes, it is edible and delicious. Unlike other corn problems, corn smut is said to taste like truffles, with a sweet, earthy, inky flavor. If it appears in your garden and you don’t want it, your local chef would love to hear from you!

To my way of thinking, if life gives you lemons, make lemonade. Or, if you are given corn smut, make quesadillas! Corn smut can be eaten raw, or added to many dishes, such as omelets, soups, sauces, meat dishes, or even desserts! As an extra bonus, corn smut is high in lysine. This means eating it with corn, or any other seed, provides a complete dietary protein.

Corn smut description
​
Also known as devil’s corn, common smut, boil smut, Mexican truffles, or huitlacoche [pronounced weet-la-COH-cheh], corn smut is a parasitic fungus that can occur on any aboveground portion of a corn plant as purplish blobs covered with papery greenish-white tissue. These fungi prefer meristem tissue and the galls are mostly seen on the ears of corn. Ear galls are significantly larger than those which form elsewhere on the corn plant.

Corn smut gets its purple color from pigments called anthocyanins. These are the same pigments found in blueberries, raspberries, and purple cauliflower. When you cook with corn smut, don’t be surprised to see the purple color change to black, because it will. Purple pigments generally don’t hold up well to heat.

Corn smut lifecycle

The corn smut fungus (Ustilago maydis) infects plant ovaries, causing kernels to swell up into large purple galls that are filled with fungal threads, called hyphae, and spores. Corn smut spores are already in the soil and can be carried on the slightest breeze or splashed water from rain or irrigation. Dry conditions and temperatures between 78°F and 93°F are all that corn smut needs to get started. Adding nitrogen or applying manure increases the chance of corn smut developing on your corn plants. Plant injuries also increase infection rates.

Corn plants try to defend themselves against corn smut by blasting the invaders with reactive oxygen (hydrogen peroxide). Sadly, from the corn plant’s perspective, this bubbling action simply spreads the smut spores.

If smut appears on your corn, fear not! Instead, harvest the galls while they are young and have the texture of a foamy popcorn, kind of firm and spongy. These moist galls are ready for harvesting 2 or 3 weeks after infection appears. As the galls mature, they turn dry and are mostly filled with unappetizing dry, black fungal spores.

Love it or hate it, corn smut is here to stay, so you may as well learn to cook with it (or sell it).

Sometimes plants grow in ways you might not expect.

You buy a seedling.

You dig a hole. You place your fingers around the stem and gently flip the pot upside down, dislodging plant and soil.

You carefully tip the leaves skyward and lower the cube of roots and soil into the hole, pulling surrounding soil into the empty space. Then you tamp down the soil with your hands, right?

Wrong!

We’ve been doing it forever but it’s the wrong thing to do and there are several reasons why.

It all starts with the conditions under which seedlings are grown.

The state of a seedling

Commercially available seedlings start out life in as perfect an environment as possible. Protected by greenhouse walls or hoop shelters, temperatures, soil, moisture levels, nutrient availability, everything is working in its favor. Add sunlight and water and those seeds germinate and start growing like crazy. Then they get loaded into flats, which get loaded onto trucks. Those trucks are dark and bouncy. Roots and leaves get rattled around a bit, before being moved a few more times to end up in new lighting, new temperatures, and environments where people pick them up and put them down, repeatedly. Finally, they get in a car, go home, and [hopefully] spend some time in quarantine before being designated some garden real estate.

​Even seedlings started at home end up in a pot that they are about to outgrow, if they haven't become root bound already.

As delicate root hairs reach the walls of their containerized world, they twist and turn, looking for more room. Eventually, all those twists and turns can get crowded and a little abrasive. Root hairs break off very easily.

Root hairs

At 1/10 the diameter of a human hair, root hairs start forming right after a seed germinates. These tiny growths profoundly increase the surface area of the root system, making the roots better at absorbing water and nutrients, anchoring the plant, and facilitating microbe interactions. When these delicate hairs break off, they can’t do their job. It is the damage done to root hairs during transplanting that causes most of the wilting associated with transplant shock.

​Water and gravity

Instead of tamping down the soil and breaking off millions of valuable root hairs, let water and gravity do the job the way nature intended: disrupted soil gets rained on, rain drops collect and make soil heavier, drawing particles down into some air pockets while leaving important macropores and micropores, that allow air, water, and roots to move through the soil, intact. Your watering can or gentle garden hose spray do the same thing. No tamping down required.

Some trees produce heavy crops each year. Other trees go back and forth between heavy bearing years and light bearing years. This is called alternate bearing.

​Also known as biennial bearing, this tendency can explain why your fruit or nut tree doesn’t produce the same amount each year. It is not caused by pests or disease. It is simply the way some trees grow, mostly.

Generally speaking, fruit and nuts are produced on long stems or on short, stubby stems called spurs. The spurs of alternate bearing trees tend to produce blossoms one year and leaves the next. This allows the tree to gather more of the sun’s energy, carrying it through its two year cycle of production. Therefore, it is not the tree, as a whole, that alternates production each year. Instead, it is the individual stems and spurs.

Other causes of alternate bearing include weather conditions, such as a heavy frost that damages the blossoms, can result in a low production year. Since resources were not used to produce as much fruit that year, the following year will tend to be a heavy production year. Some trees may even take two years off after a particularly heavy year. In other cases, mineral deficiencies or excessive fertilization, especially nitrogen, can result in a cycle of alternate bearing to begin.

Most perennial fruit crops start making fruiting buds during the previous season. If conditions are especially good or bad, those developing buds will become stronger or weaker, respectively. There is also some research that suggests the developing ovules of a heavy production year produce hormones that inhibit next year’s flower production. Scientists are still learning the details about what causes alternate bearing.

Some commercial growers reduce the impact of alternate bearing trees by thinning blossoms and fruit on heavy production year. This is done to counteract the fact that fruit produced during heavy years tends to be smaller, while fruit produced during low production years tends to be of poor quality and more susceptible to pest and disease damage. Evening things out improves crop quality and tree health.

Citrus, apple, pear, avocado, apricot, plum, mango, cranberry, blueberry, olives, pecan, and pistachio are common plants that exhibit alternate bearing behavior in the home garden. Grapes almost never do.

You can reduce the negative impact of alternate bearing on your fruit and nut trees with proper pruning, irrigation, and feeding, along with regular fruit thinning, soil tests, and protective treatments against pests and diseases.

Now you know.

Plant a seed at the proper depth and it thrives. Plant it at the wrong depth and it dies. So, how is a gardener to know how deep to plant each seed?

The general rule of thumb for seed planting depth is to use twice the seed width or diameter. This means a seed that is 1/8” wide should be planted 1/4” deep. Too often, seed packets rely on a standard 1/4”  or 1/2” planting depth, which is not always in a seed’s best interest. ​​

A seed’s life

Once a seed reaches maturity, it is protected by a hard outer shell called its seed coat. This layer allows the seed to roll, float, fly, or pass through a digestive system unscathed and ready to germinate. Only when heat, light, and moisture levels reach the right combination can the seed coat allow moisture in, which triggers the growth of the embryo within. Hopefully, the seed is at the proper depth to grow into a healthy plant.

Planting seeds too deeply

Seeds planted too deeply are less likely to germinate or sprout. Even if they do get that far, those seedlings have to work harder to reach the soil surface. This uses up valuable energy resources that should have been available for producing leaves and stems. It also reduces their growing season.

The very tiniest seeds should simply be sprinkled on the soil surface and only dusted with a covering of soil or vermiculite. And a few seeds, such as lettuce and dill, actually need light to germinate, so they should not be covered at all.

Planting seeds too shallowly

At the other end of the planting depth spectrum, seeds planted too shallowly end up with roots too close to the surface, causing them to wither and die. Even if they don’t die, shallow roots are less able to take up water and nutrients or to anchor plants in the soil. Seeds planted too shallowly are more susceptible to temperature and moisture level changes. These plants are also more likely to bolt, rather than producing a crop.

Seed planting depth also depends on soil structure. Seeds planted in rich, loose loam or sandy soil can tolerate deeper planting than seeds planted in heavy, compaction-prone clay. 

Crops by seed depth

Here is a list of some of the more popular garden plants and their proper planting depths:

•     1/8 to 1/4 inch - celery
•     1/4 inch - arugula, broccoli, cauliflower, peppers, radish, tomatoes
•     1/4 to 1/2 inch - cabbage, carrots, eggplant, onion
•     1/2 inch - beets, cucumbers, melon, spinach, Swiss chard, watermelon
•     1 inch - pumpkin, squash
•     1 to 1-1/2 inch - soybeans
•     1 to 2 inches - beans, peas
•     2 inches - corn
•     3 to 4 inches - potatoes

Tools, such as a dibble, can help ensure that seeds are planted at the proper depth.

Finally, do not press down on the soil once a seed is in place. This compacts the soil. Instead, the act of watering will tuck your seeds in nicely while still giving them a chance to grow and thrive.

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.

Flower anatomy

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. ​

Pollination

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.

Advantages of grafting

It is pretty safe to assume that nearly all fruit and nut trees available today are grafted combinations of hardy, pest- and disease-resistant rootstock and highly productive scions. 

Grafting speeds up production because young scions can be grafted onto older rootstock. This is called precocity and it allows growers to skip the 5- to 12-year juvenile phase, when trees are focusing on root system development, rather than fruit production. Grafted trees can also selected for size. Simply graft a scion from a full-sized tree onto dwarf rootstock and you get a dwarfed tree that produces more fruit. In many cases, grafting is used to imbue a tree with pest or disease resistance. This method is also used on watermelon, tomato, eggplant, cucumber, and other vegetative plants for the same reason.

Grafting for the garden

Let me say this up front - grafting requires skill. It easy to do incorrectly. There are several factors that contribute to successful grafts, and all of them are important:

• Compatibility - Clones and members of the same species are the easiest to graft because they have identical structures [peach to peach]; two different species within the same genus can sometimes be grafted [peach to cherry]; plants in the same family, but different genera can only occasionally be grafted successfully [peach to apple]; monocots, because they lack vascular cambium, cannot be grafted.
• Alignment and surface contact - The vascular bundles of both the scion and rootstock must be in firm contact with each other, and oriented in the same direction.
• Timing - Successful grafting occurs when the scion is dormant, the rootstock is able to produce a protective callus, and temperatures are not too warm or too cold. In the Bay Area, most grafting is done January through March. 
• Site protection - Graft sites must be protected against dehydration, pests, such as vine mealybugs, and diseases until they have healed. This means using very sharp cutting tools that have been sanitized frequently throughout the process. Tapes and waxes are commonly used to seal the grafting site. Structural supports may also be needed.

Tools used in grafting

Having your tools ready ahead of time will increase your odds of successful grafting. The last thing you want is for plant tissue to dry out before you are done. [Many gardeners hold scions in their mouth as they work, to keep the plant tissue moist.] You will need sharp, sanitized pruning clippers, stretchable, biodegradable grafting tape, a sharp grafting knife, and sanitizer. You may also want to have some tree sealant or grafting wax handy.​

Autotoxicity is a form of chemical warfare found in the plant world, and it might be happening in your garden or landscape. Or, it might be an unsubstantiated biological process that looks great on paper, or works out well in a laboratory petri dish, but doesn’t hold as true in the field.

In either case, it is good know what the concept claims, which parts have withstood the tests of time and science, and how it might impact your garden. Let’s start with basic competition for survival.

We know that plants compete with their neighbors for real estate and resources. Those resources include water, sunlight, nutrients, beneficial soil microbes, and access to pollinators. Over time, plants have found different ways to gain an edge over the local competition. Many weeds have evolved to grow faster, in order to find resources first, while other plants grow taller, to commandeer available sunlight. Other forms of competition occur when plants develop deeper or wider spreading roots, which can reach more food and water, or more flamboyant, heavily scented flowers, to increase pollination rates. In some cases, plants have evolved to use chemicals on their neighbors.

Chemical warfare among plants

​Oblivious to the Geneva Convention, some plants release chemicals through their roots, leaves, and stems that impact neighboring plants. When those chemicals affect other species, it is called allelopathy [al-el-ah-path-ee]. Allelopathic plants release chemicals that can either stimulate or inhibit the life processes of other plant species. When those chemicals only affect plants of the same species, it is called autotoxicity. Autotoxicity can only inhibit, and never stimulate, the growth or germination of plants of the same species. But why would a plant want to treat family members that way?

Family feud

The word ‘autotoxicity’ means ‘self-poison’ and it is used to describe the way some chemicals are believed to only negatively impact plants of the same species. From a survival perspective, on the surface, this might make sense. Members of a species all need the same resources to thrive. If there are too many of one species growing in the same place, those resources can be used up before any individual plant has time to reproduce, except that it isn’t that simple. Let’s take a closer look at which plants are said to be autotoxic and how autotoxicity is said to work.

Autotoxic plants

​Alfalfa is acknowledged as an autotoxic plant. How can this be, you might ask. Alfalfa is grown in immense fields, the same way corn, oats, and other similar crops are grown, with other alfalfa plants on every side, isn’t it? It is. But, underground, soon after alfalfa seeds germinate, seedlings start producing toxins that reduce germination and prevent the growth of root hairs in other alfalfa plants. Without root hairs, neighboring plants cannot absorb water or nutrients. So, why aren’t all the nearby alfalfa plants dead?

​The trick lies in the fact that these chemicals are not released until the seedlings have gone through their full lifecycle and died. As the plants were busy maturing, the levels of these toxins continued to increase, but those chemicals only impact the next crop, as the dead plant material decomposes. Because of this, crop rotation is commonly used when growing alfalfa commercially.

According to one Canadian study, several other edible plants are said to be impacted by autotoxicity. Their list includes asparagus, citrus, tomatoes, rice, wheat, corn, cucumber, ginger, soybeans, sugarcane, muskmelon, watermelon, tea, and coffee. The problem with the science behind autotoxicity lies in the fact that some of the chemicals cited as autotoxins, such as p-coumaric acid, are found in many other plants, with no ill effects. Also, in much of the current research, autotoxic chemicals are applied artificially, which may or may not involve all the steps that might occur in nature.

Autotoxic compost?

When we apply compost to an area of the garden or landscape, we are introducing a variety of chemicals. In the case of small home gardens, the diversity of plant materials found in a compost pile generally reduces any potential autotoxic affect to negligible levels. Using no-dig gardening and cutting used up plants off at soil level, rather than pulling them out by the roots, leaves these potentially autotoxic roots in the soil. This may or may not create a problem, but it is something to keep in mind.

Whether autotoxicity is a real problem or not, you now know more about it than most people. And remember, before you accept opinion as gospel, make sure there is enough good science behind it to make it worth your time and effort.

Yeasts have been around for hundreds of millions of years. In many ways, yeasts and other fungi are a lot like plants, but they are different in many ways, too.

Yeast vs. plant cells

Yeast cells are smaller than plant cells. While plant cells can become leaf, stem, fruit, or root cells, yeast cells remain the same one-celled creature. Like plant cells, yeast cells have a cell wall, but it is not made out of cellulose. Both yeast and plant cells have membranes, but they are made out of different materials. Yeast cells do not have chlorophyll-producing chloroplasts, either, which is why they do not use sunlight to make food. Inside a plant cell, you can find food stored as a starch, whereas yeasts store food as sugar. 

Other common fungi include mushrooms and molds. The yeast you buy in the store to make bread, beer, or wine is called Saccharomyces cerevisiae.

How do yeasts grow?

Yeasts do not require sunlight to grow. Yeasts feed on dead, decaying matter, making them saprophytes. They are also parasites, which makes them heterotrophs. Instead of using the sun’s energy to generate food, fungi absorb carbon, in the form of sugars, organic acids, and other easy-to-digest carbon-based edibles from their hosts. This is why you will often see fungi growing on the skins of apples, grapes, or peaches. Yeasts grow best when the environment has a neutral or slightly acidic pH. ​

Yeasts reproduce in a variety of ways, depending on the species and environmental conditions. The most common method of yeast reproduction is an asexual, vegetative method called budding. In budding, a clone offspring is produced as an attachment to the parent cell. When the clone, also known as a bleb or daughter cell, reaches maturity, it separates from the parent cell, leaving behind scar tissue. In some cases, these buds can link themselves together into chains, called false hyphae. Other yeasts reproduce using mitosis. In mitosis, the genetic information is duplicated and the nucleus of the cell is split in half, with each half being a twin to the other. Fission and meiosis are also used by some yeast species, but we digress

​Harmful yeasts in the garden

Yeasts love to eat sugar. As such, they can spoil fruits and vegetables before you ever get a chance to enjoy them. Yeasts can grow on almonds, pineapples, lettuces, and pretty much anything else you decide to grow. Peach leaf curl is also caused by a yeast. That being said, yeasts actually perform many beneficial services to your garden.

Most fruit and nut trees available today are actually two different plants that have been grafted together. Where those two plants come together is called the graft union, or graft collar.

Graft unions are usually easy to spot. They tend to be lumpy, raised areas. The shape of the graft union depends on the type of graft used to merge the two plants.

Grafting

People have been cloning plants with grafting for thousands of years, and this method of plant propagation is not limited to trees. Your store-bought tomatoes and other vegetables may also have been grafted.

​Grafting is done by inserting a shoot or twig, called the scion, into a slit cut into the trunk or stem of another plant, called the rootstock. This allows the vascular bundles of the two plants to merge, allowing water and nutrients to move between the two.

​Grafting allows us to take advantage of one plant variety’s strong root system and another plant’s heavy fruit, nut, or flower production. Grafting allows us to select plants for their combined characteristics of size, hardiness, growth habit, growth rate, disease and pest resistance, and flavor.


The name of the plant you buy usually refers to the aboveground portion of the graft, though you may also see mention of the rootstock. Grafting is what allows you to have a tree that produces multiple varieties of fruit. These graft unions are found higher in the tree canopy.

Bare root trees

Bare root trees commonly start appearing in garden centers in January in the Bay Area. If you shop from knowledgable, reputable growers, the plants they have available will be suited to the local climate. If you are shopping bulk discount stores, well, you may be getting something else entirely. Wherever you get your fruit and nut trees, be sure to inspect the graft union for signs of damage, disease, vine mealybug nymphs, and other insects. Graft unions are delicate, vulnerable areas. Until relatively recently, it was suggested that the graft union be positioned below soil level. We now know that this is a really bad idea, leading to several problems.

Graft union problems

Improper planting depth is currently the primary reason why trees fail. Part of this is due to bacterial and fungal diseases entering the tree through the graft union, causing root rot, crown gall, and phytophthora root and crown rot, among others. These problems can be avoided by ensuring that your plants are installed at the proper depth. This generally means that the graft union will be 2 to 4 inches above the soil level, or more. [The higher the graft union, the smaller the mature tree will become.] If stem growth starts occurring below the graft union, it is called graft union suckering. 

Graft union suckering

Graft union suckering occurs when the graft is less than successful. These suckers start growing out of the root stock portion of the stem, which may sound fine for the root system, but it is bad for the overall plant. Very often, rootstock plants are highly susceptible to aboveground pests and diseases, and they rarely produce desirable crops. If graft union suckers appear, remove them as close to the branch collar as possible, without damaging the collar.

Take a closer look at the trees, shrubs, and other plants in your garden. Do you see any graft unions? Are they above the soil line? I hope so!

Girdling roots

Girdling roots are those lateral roots found just below the surface that have, for one reason or another, started growing in circles around the tree. This is common with trees kept in containers for too long. Another common way girdling roots occur is when the roots are ‘spun’ into the planting hole, rather than spread out horizontally. Make sure that your planting hole is wide enough to allow those important roots to spread out the way they were meant to grow. ​
​
Girdling roots can also occur in compacted soil. If the surrounding soil is compacted, young roots simply cannot penetrate, so they go around and around, looking for a path in their search for moisture, minerals, and air. Curbs, large stones, and building foundations can have similar effects. Girdling roots will kill your tree in 5 to 15 years. It won’t matter how well you fertilize or irrigate your tree.

Speaking of irrigation, be sure to avoid standing water around the trunk of your tree. This can lead to crown rot and other fungal diseases. Instead, use soaker hoses or build an irrigation ring at the tree’s drip line.

Are your trees planted properly?

The easiest way to tell if a tree is planted properly is to dig down an inch or two, with your fingers, next to the trunk. You should come across 4 to 11 substantial roots. If all you find are delicate feeder roots, your tree is planted too deeply. If the roots are visible from the surface, it is too shallow.

How to correct planting depth errors

Trees planted too deeply (below grade) should be dug up, the roots inspected, and then replanted at the proper depth. Trees planted above grade need more soil added around the trunk. First rake the area under the tree to loosen the existing soil. Then add a layer of soil to the proper depth, gently sloping away from the trunk. 

Proper planting depth is critical to your tree’s health. Trees planted above or below grade will never thrive. Believe me, it is much easier to do it right in the first place.