You’ve seen the words, but what do partial sun and partial shade mean? Are they the same thing? Sun exposure is an important part of knowing where to put your plants.
Without sunlight, most plants can’t grow. Plant labels and plant descriptions often give you information about the amount and intensity of sunlight a plant needs, but the terms can be a little confusing.
Some yards receive more sunlight than others. Knowing how much sunlight an area gets can help you select the right plants for that space. Keep in mind that some plants can grow in more than one type of sun exposure.
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). Full sun plants are your go-getters. Most summer crops prefer full sun. Artichokes, cucumbers, eggplant, fruit and nut trees, peppers, squash, tomatoes, and most herbs need 8 to 10 hours of direct sunlight each day. Plants with silver or gray foliage also prefer full sun.
Partial sun means 3 to 6 hours of sunlight in the afternoon. Partial sun is 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 in the day. Artichokes, asparagus, beans, beets, blackberries, broccoli, cabbage, carrots, cauliflower, chives, leeks, cilantro, garlic, kale, lettuce, melons, mint, onions, oregano, peas, potatoes, radishes, raspberries, rutabagas, Swiss chard, and turnips can be grown in partial sun.
Partial shade means 3 to 6 hours of morning sun with protection from more intense midday and afternoon sun. These are your early risers. Artichokes, arugula, asparagus, beans, blackberries, bok choy, Brussels sprouts, cauliflower, endive, garlic, kale, lettuce, mustard greens, onions, radishes, raspberries, spinach, and Swiss chard grow well in partial shade.
Before you start sticking plants in the ground, you should probably create a sun map of your yard. This will tell you how much sunlight each area actually gets. And remember, those areas change with the seasons. Also, the plants themselves can create different degrees of shade or exposure for other plants. I grow chives under my artichoke plant. This is a form of companion planting, or intercropping.
If you have a garden with traditional rows, your plants will get the most sun exposure if your rows are oriented in north-south directions and your tallest plants are at the northern end of your garden plot.
How deep do roots go? Rooting depth is dependent on a lot of different conditions. After reading this post, you may never look at your garden plants the same way again. I know I don't!
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.
In my case, I have to assume that plants installed directly in the ground are going to have a tougher time moving around in the soil, for at least another year or two. Because of this, I try to remember to install shallow-rooted plants in those places. I generally use my 12” deep raised beds for plants with moderately deep roots and my 24” deep bed for the plants with deeper roots, though not always. Because my raised beds are open to the native soil at the bottom, rooting will get progressively deeper as the preexisting soil improves.
Strawberries are classified as shallow-rooted, but my deep bed has newly built netted panels that keep birds away, so that’s where my strawberries live. [As you read this post, you will learn that strawberries are not nearly as shallow-rooted as many, myself included, once believed.]
Listed below are categories of minimum rooting depths, under ideal conditions, for many common home gardening plants. Remember, these numbers are bare minimums, assuming nutrient-rich, loose soil. Your results may vary.
Shallow rooted plants
These plants are your best choices for containers, towers, and compacted soil. Basil, chives, cilantro, endive, escarole, ginger, lettuce, oregano, parsley, radish, scallions, spinach, summer savory, tarragon, and thyme can all be grown in less than 12” of soil. Of course, more is generally better. In one study, biologists found that “doubling plant pot size makes plants grow over 40 percent larger.” And look what happens to a lettuce plant, given its freedom to grow! [By the way, the squares in all of these illustrations are one foot by one foot.]
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.
Artichokes, cantaloupe, cardoon, cereal grains, citrus, figs, lima beans, melons, parsnips, peaches, pumpkins, sage, squash, tomatoes, and watermelon need 24" of loose, nutrient-rich soil.
Deep rooted plants
Your asparagus, cherries, fava beans, hops, olives, pears, prunes, rhubarb, and spring wheat will ultimately go down 3 feet or more. Alfalfa, almonds, apricot, and corn may have roots that are 4 feet long, while walnut trees and winter wheat may reach 5 feet. The roots under your grape vines may be 20 feet long.
Remember what I said earlier about strawberries? Well, if you are like me, strawberry pots have never seemed to work out. Believe me, I’ve tried! Experts all say strawberry plants have a minimum rooting depth of 12”. What they don’t tell you is that mature plant roots might go down 3 feet! And what about that containerized horseradish? A 10-year old horseradish plant may have roots as deep as 14 feet!
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.
Vines - we know what they are, but what makes a vine a vine, and how are they unique?
In some places, the word “vine” is only used to refer to grapevines. But kiwifruit grows on vines. Pumpkins, watermelons, cucumbers, peas, and pole beans also grow on vines. Or do they?
Types of vines
Climbing plants use a variety of methods to reach the sun. They can be climbing or trailing woody-stemmed or herbaceous plants. In general, we call them all vines. Stems tend to be very long and often lack the supportive tissue needed for upright growth. This allows plants to grow upward without the same investment of energy and resources used by trees and other self-supporting plants.
To the purists, grapes grow on vines, all other woody climbers are lianas, and our pole beans, peas, and cucurbits are herbaceous vines.
Now you know.
Your chewing gum is made from trees. Well, it used to be.
Tree gums have been used as a chewable treat for over 9,000 years. Mayans and Aztecs used gum from the chicle tree. Ancients Greeks used gum from the mastic tree. Native Americans used gum from spruce trees. It was the Americans, however, who make chewing gum famous to the point that there were not enough trees to produce the gum needed to make gum. It is estimated that over 100,000 tons of chewing gum are consumed each year. Most modern chewing gum is made with natural and/or synthetic rubber and not botanical gums.
But gum isn’t the only goo produced by plants.
Plants ooze several different substances. Gum is only one of them. Plants also produce fats and oils, latex, mucilage, resin, and waxes. The fats and oils produced by plants are more commonly known as essential oils. Essential oils can be responsible for a plant’s unique smell or flavor. Latex is the milky white emulsion of defensive chemicals seen oozing from broken dandelion stems. Mucilage is used to store food and water, thicken membranes, and in seed germination. Succulents and flax seeds have particularly high mucilage contents. Resin is a viscous mixture of antibacterial, antimicrobial acids commonly seen in conifers. Resin dries to a hard, crystalline structure. And then there is plain old sap.
Sap has different components, depending upon where it is found. Xylem sap carries water, hormones, and minerals from the roots to the leaves. Phloem sap conducts sugars, hormones, and minerals from leaves, where carbohydrates are produced through photosynthesis. Sap generally stays fluid. Gums are a specialized type of sap produced by woody plants.
[Plum gum? Sorry, I couldn't resist.]
How do plants use gums?
Gums are produced in a process called gummosis. Gumming refers to the way some plants can break down internal tissues, particularly cellulose, to create a high-sugar sap, or gum, used to seal off wounds and surround invading insects. Gums are commonly found in conifers, such as pine and spruce. Some plants, such as Western poison oak, use gums as protective, gummy seed coatings that delay germination.
How do we use botanical gums?
Botanical gums are water-soluble sugars that are commonly used in the food industry as emulsifiers, thickening agents, and stabilizers. They are also used as adhesives, in printing, candy-making, paper-making, and to make chewing gum.
If you look at ingredient lists on packaged food (and I urge you to do so), you may see some of these botanical gums:
Gums are frequently collected by tapping or otherwise wounding trees with incisions or by peeling back sections of bark. The trees respond to these wounds by gumming.
Tapping is the method used to collect the sap from sugar maple trees to make maple syrup. A tap consists of a metal tube with a downward-pointing lip and a notch or hook from which to hang a bucket. The tube end is hammered into a tree to reach the xylem and a bucket hung from the lip. Sap from the xylem flows (very, very slowly) through the tube, down the lip, and into the bucket. From there, the sap is cooked down to reduce the water content. More modern set-ups use plastic tubing. My students and I once made a delicious syrup/caramel from silver maple trees.
Some of these gums stay soft, while others harden into “tears” which are broken off for processing. If you see gums oozing from your trees, take a closer look.
Why do some fruits continue ripening after being harvested, while others do not? It all depends on whether or not they are climacteric.
Ripening is a highly complex developmental process. It is largely dictated by plant genetics and partially affected by climate. As fruits ripen, distasteful flavors are broken down, sugar levels and other pleasant flavors increase, pectins soften, acid and carbohydrate levels change, colors change, and a lovely aroma is released. One of the most important players in the ripening process is ethylene gas.
Ethylene gas is a plant hormone produced by nearly all fruits. It is used in response to injury and to ripen some fruits. Climacteric fruits have very sensitive ethylene gas receptors. It doesn’t matter whose ethylene gas it is. Once these receptors are triggered, a domino effect of ripening is activated: respiration and ethylene gas production spike, whether or not they are still attached to the parent plant. Increased respiration and ethylene gas drive the ripening process in climacteric fruits.
Ethylene gas is the reason why bananas or apples stored near other climacteric fruits will cause them to ripen faster. It is also why bananas are now sold with plastic or wax over the stem ends - to reduce ethylene gas emissions.
Non-climacteric fruits also produce ethylene gas, but at much smaller rates. These fruits rely on other methods of ripening. This is a new area of study and very little is known at this time except that auxins and abscisic acid are believed to play critical roles.
Which fruits are climacteric?
Apples, apricots, avocados, bananas, blueberries, cantaloupes, figs, kiwifruit, mangos, nectarines, papayas, peaches, pears, pineapple guava, plums, tomatoes, and some hot peppers are climacteric. This means they can be removed from their parent plant and will continue to ripen.
Bramble fruits, such as 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.
Whether a fruit is climacteric or not, leaving it on the parent plant for as long as possible is the only way to get the best flavor and nutritional value.
After the climacteric stage has been reached, plant respiration returns to normal or below normal and fruits become far more susceptible to fungal infections. In other words, after climacteric (and non- climacteric) fruits have reached their peak of flavor and sweetness, they start to rot.
Now you know.
Very often, you can propagate new plants from old ones by taking a piece of the parent plant and giving it a warm, moist place to grow. This works because plants have undifferentiated cells that can become any part of the plant. Given the right conditions, meristem tissue that was going to become stem or leaf can develop into roots instead. Vegetative propagation can take several forms.
Many houseplants are propagated by cutting off a stem and sticking it in water until roots appear. Succulents are particularly well suited to propagation by cuttings. Simply break off a leaf and stick it into some soil. Cuttings can be taken from leaves, stems, and roots and coaxed into producing new plants with varying degrees of success. Some plants root faster and more easily than others. Generally speaking, woody stems are more difficult to propagate with cuttings than soft-stemmed plants.
Many bulbs and perennial plants benefit from being divided every few years. This happens because the root system can become overcrowded. Artichokes, chrysanthemum, germander, saffron crocus, and yarrow often benefit from being divided. If you dig up one of these plants, you can pull or cut them into smaller portions and replant elsewhere. Division is normally done in autumn, unless it is an autumn-blooming plant, such as saffron crocus, in which case division is performed in spring. Autumn temperatures give plants time to recover and develop new root systems.
Strawberry runners are an example of layering. Layering is a method in which portions of a plant are bent to the ground and covered with soil while still attached to the parent plant. The parent plant provides water and nutrients needed by the daughter plant until roots emerge from the soil-covered nodes. Once the clone is established, it can be separated from the parent plant. In many cases of layering, the section of the plant touching the soil is purposely wounded to stimulate rooting. There are six types of layering: air, simple, compound, tip, and trench methods.
Scions are young twigs cut from parent plants, usually trees, which are then grafted onto other trees. The meristem tissue found within the scion dictates what sort of blossoms and fruit will be produced. Scions are what make “fruit cocktail” trees possible. These are trees that produce a variety of fruits. You can have a single citrus tree that produces Valencia and Navel oranges, kumquats, grapefruits, and tangerines, or you can have a stone fruit tree that produces peaches, nectarines, apricots, and almonds.
Suckers and root sprouts
Suckers are shoots that occur at the base of a tree or shrub. Root sprouts come up from the root system, usually at a distance from the parent plant. 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:
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.
Root sprouts appear to be random baby trees or shrubs that keep popping up in your landscape. Getting rid of them can be difficult.
Many plants pass on their genetic information through seeds. Seeds are spread by birds, the wind, people, and herbivores. Plants can also propagate themselves vegetatively using suckers, adventitious shoots and root sprouts. These growths emerge from adventitious buds, which occur close to the vascular bundle, where they will have easy access to water and nutrients. The different names refer to where they occur. Suckers, also known as basal shoots, occur at the base of a tree or shrub. Adventitious shoots can form on stem internodes, leaves, roots, or callus. Root sprouts emerge from the root system.
Root sprout growth
Root sprouts often grow out of adventitious buds found on a tree’s extensive root system. Root sprouts are clones of the parent plant.They can be found a significant distance from the parent tree. Root sprouts can also grow from the roots of a tree that has fallen or been cut down. Apple, cherry, and guava are especially prone to root sprouts.
If a plant produces root sprouts, it is said to be surculose.
Root sprouts can be used to propagate new plants. They also use up a plant’s energy stores and can make a mess of your lawn or landscape. They are also responsible for one of the world’s biggest and oldest life forms.
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:
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.
We all know what tree branches are, but what are scaffold branches and why are they important?
What are scaffold branches?
Trees have an underground root system, a trunk, primary branches, secondary branches, and so on. Both above and below ground, the fractal splitting of growth creates ever-smaller and more delicate parts. Twigs emerge from lateral branches and lateral branches grow out of primary scaffold branches. Scaffold branches are the heaviest limbs which create the structure of a tree’s canopy, or silhouette.
Scaffold branches and pruning
Pruning and tree training are the best way to ensure your trees are healthy, safe, and productive. Before putting your tree saw to work, you need to know about scaffold branches.
Mature scaffold branches are rarely pruned or removed, unless they are severely damaged or diseased, as they provide the overall structure of a tree’s shape. Young trees, however, must be trained into forms that allow for proper sun exposure and air flow while maintaining branches that are less likely to break once burdened with lateral branches, twigs, leaves, and heavy fruit crops.
The angle at which branches attach to one another, known as the angle of attachment or the branch axil, determines the strength of that connection. Angles of attachment that are too narrow become areas of weakness later on. These V-shaped crotches also provide overwintering sites for American plum borers, prune limb borers, and many other pests. Branch axils of 30° or more generally result in sturdy attachments that can withstand strong winds and heavy fruit or nut crops. Downward hanging branches are highly prone to breakage. The best branch axils are 45° to 60° angles.
Selecting scaffold branches
When training young trees, you want scaffold branches that are appropriate to the species, spaced properly, and at good angles. You should avoid having more than two scaffold branches at the same distance from the ground. Scaffold branches should be at least 8” to 16” apart, vertically. Also, select scaffold branches that are positioned radially around the trunk so that they are not growing directly above or below each other.
As you train your tree, remember to avoid cutting the branch collar and do not use sealants. Sealants often trap moisture against the wound and create the perfect environment for rot. Your tree knows how to heal itself and will form callus tissue over and around the wound.
Take a look at the scaffold branches on your trees. Are they strong and healthy or do you need to do some re-training this dormant season?
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:
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:
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:
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.
Chlorine in your plants? Yes. Well, sort of.
Before you go grab a jug of bleach, you need to know that laundry bleach most commonly refers to a dilute solution of sodium hypochlorite. This is NOT something you want anywhere near your plants. In fact, high concentrations of chlorine are fatal to all living things. It was even used in World War I as the first chemical warfare agent.
We are not quite ready to throw the book at chlorine, however. We need to know that chlorine is an element, much like copper or nitrogen, used by plants as food. You don’t hear much about it because plants only need it in tiny amounts. Once called trace elements, minerals used in such small amounts are now referred to as micronutrients. The form of chlorine used by plants is called chloride (Cl-).
Forms of chlorine
Chlorine is a highly reactive element. As such, it rarely occurs naturally by itself. Instead, it binds to other, nearby elements. In fact, chlorine will pair with practically every other element in the Periodic Table. Those parings occur because chlorine most commonly exists as an anion, or negatively charged, somewhat unstable atom, called chloride. To stabilize its outer electron field, chloride shares electrons with other elements, creating molecules. Some of these more familiar ‘binary chlorides’ include:
We all know ‘salting your fields’ ends badly for plants. Unfortunately, it can be difficult to know just how much chlorine is in your soil. Most soil tests do not include chlorine results. If your soil test indicates excessive levels of other anions, such as sulfur and boron, it may be difficult for your plants to absorb the chlorine they need. Only a lab-based soil test can tell you what those levels are and how they are changing over time. If you see signs of chlorine toxicity, you may want to limit the use of calcium chloride and potassium chloride.
How plants use chlorine
Chlorine aids plant metabolism during photosynthesis. It is necessary for osmosis and fluid balance within plants, working in tandem with potassium ions to open and close the stoma. As an anion, chlorine binds with many cations, or positively changed ions, helping to transport them throughout a plant. Chlorine also appears to have antifungal properties which are currently being explored.
Chlorine toxicities and deficiencies
Chlorine is a relatively mobile nutrient, which means it moves around freely within a plant, going wherever it is needed. This means that deficiencies are most often seen in older growth. Chlorine deficiencies appear as wilting, leaf mottling, and a highly branched but stubby root system. [Cabbages that are grown in chlorine deficient soils do not smell like cabbages.]
More often, chlorine toxicities occur close to swimming pools and in areas with hard water. [San Jose tap water ranges in pH from 7.0 to 8.7.] Symptoms of chlorine toxicity appear as scorched leaf margins, excessive leaf drop, reduced leaf size, and reduced overall growth. Too much chlorine can also interfere with nitrogen absorption, causing chlorosis, or yellowing, but that might not always be a bad thing.
We know that new growth tends to be more susceptible to disease than older growth. It ends up that chlorine’s interference with nitrogen uptake may be a method of reducing disease severity. As a disease occurs, plants absorb more chloride anions, blocking nitrogen uptake, and reducing the amount of vulnerable new growth being produced.
Now you know.
Gymnosperms are plants that produce naked seeds. We say they are naked because the seeds are not surrounded by an ovary. When seeds are enclosed by an ovary, which we generally refer to as fruit, the plant is classified as an angiosperm.
Angio- or gymno-?
There are several differences between angiosperm and gymnosperm:
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:
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!
The red juicy bits found inside a pomegranate are called arils. Arils are a type of accessory fruit, or false fruit.
True fruits and false fruits
Fruit is the tissue that surrounds the seeds of angiosperms (flowering plants). Fruit is made from a plant’s ovary. Except when it isn’t. In some cases, a fruit develops from both the ovary and nearby tissue. These tissues can be either the perianth (flower whorls) or the hypanthium (the flower base). When this occurs, the part we eat is called an accessory fruit, or false fruit. Common accessory fruits include figs, mulberries, pineapples, and strawberries. Arils are specialized versions of these false fruits.
Arils are outgrowths that cover seeds partially or fully, which may or may not turn in to an edible fruit. This outgrowth originates where the seed attaches to the ovary, at the hilum. Along with pomegranates, the spice known as mace is an aril. Mace is a striking red aril that surrounds a nutmeg.
A slightly different version, called an arillode or false aril, emerges from a different location on the seed coat. Lychee, for example, grows partly from the hilum and partly from the integument or coating of the seed. The same is true for soapnuts. And yew creates a cup-shaped aril fruit, rather than a traditional cone.
Like other fruits, the aril serves as an attractant to herbivores. As birds, animals, and people eat these fruits, the seeds are spread farther and wides, improving the odds of continuing that particular line of genetic information.
Now you know.
Root hairs are where water absorption occurs. Since that water contains nutrients found in the soil, root hairs are important. And fragile.
You might expect root hairs to grow along the entire length of a root system, but that’s not what happens. Root hairs only occur in specific areas, or zones, of a root system.
Roots start out as undifferentiated cells. The very tip of a root is called the root cap, which protects the growing root as it moves through the soil. The next zone is where cell division takes place. As more cells are produced, the root cap is pushed forward. This growth is a relatively continuous process throughout the life of a plant. As new cells are produced and the root moves forward, the older cells stretch and create storage pockets called vacuoles. This is called the zone of elongation. Finally, growth and elongation are complete and root hairs can begin to emerge. This is called the zone of maturation.
The reason root hairs do not appear right away in the growth process is because they are so delicate that they would be sheared off as the root moves through the soil. This is also what causes transplant shock. The act of transplanting can shear off a majority of the root hairs as the soil gets jostled about and uninformed gardeners tamp down the soil. Rather than crushing delicate root hairs, mudding in new transplants protects those important root hairs.
Did you know that the reason root hairs are so evenly spaced along a root is because each hair secretes a poison that prevents nearby cells from producing their root hair? I didn’t either.
How root hairs absorb water and nutrients
Nutrient-rich water is pulled into the cytoplasm of root hair cells by osmosis. Root hairs also secrete malic acid, which helps convert minerals into ionic forms that are easier to absorb. Organic molecules in the soil, called chelates, also help root hairs absorb nutrients.
Root hairs as defense mechanism
Because root hairs are so small, they make it very difficult for harmful bacteria to enter the plant through the xylem. When beneficial bacteria, such as those which help legumes fix atmospheric nitrogen, appear, root hairs curl around the welcome visitor. This allows an infection thread to connect the two for everyone’s benefit. Helpful soil microorganisms, called mycorrhizae, are small enough to enter a plant’s root system through the root hairs. Root maggot larvae feed on root hairs.
Plants use phosphorus to grow healthy roots. Before you add more phosphorus to your soil, be sure to send out a sample for a soil test. Too much phosphorus can be just as bad, or worse, than not enough.
Nurse cropping is a form of companion planting in that specific plants are installed to provide one type of protection or another for young crops as they become established.
Nurse crops protect young perennials
In commercial agriculture, nurse crops are fast-growing annuals that are planted along with perennials, such as alfalfa, to help those perennials become established. This gives the long term crop protection from pests as it is getting started.
Nurse crops as trap crops
Trap crops are installed around or near desirable crops because of the way they attract or repel specific pests. In some cases, trap crops interfere with a pest’s lifecycle or kill it outright. In other cases, the trap crop is “harvested” after pests have appeared to remove them from the garden.
Nurse crops are frequently used as traps crops. For example, wireworms are a big problem for strawberries. In one study, strawberries planted alone had a 43% mortality rate, while strawberries planted two weeks before wheat was added had a 27% mortality rate. When wheat was planted 8 days before the strawberries, that mortality rate dropped to 5%. That’s a significant savings in strawberry starts, just by broadcasting a handful of wheat berries a week ahead of time!
Pros and cons of nurse cropping
Like every other plan of action, nurse cropping has pros and cons. The benefits of nurse cropping include reduced weeds, wind and erosion. Also, perennial seedlings are protected from excessive sun in their first weeks of growth. Oats and other cereals are common nurse crops. As such, another benefit is that the nurse crop can be a harvestable edible in its own right.
The potential problems associated with nurse cropping is that the nurse crop does use up water and nutrients. It may also become a type of weed itself.
You can use nurse cropping in your garden by starting cereal grains in a bed a week or so before planting something else. If you don’t harvest it, the local birds and other wildlife will appreciate the buffet and more tender plants will benefit, as well.
The way veins are arranged on a plant leaf can tell you a lot about that plant. That pattern of arrangement is called venation or veination.
There are complex classification systems for leaf venation, but all you really need to know is that there are four basic patterns: pinnate, palmate, parallel, or dichotomous.
Pinnate venation looks like a feather, with the primary vein emerging from the center of the base of the leaf and smaller veins, called veinlets, occurring at intervals and pointed outward at an angle. Pinnate venation is seen on citrus, walnut, and pistachio.
Palmate venation looks more like a hand with three or more veins radiating from the base. Grape, pumpkin, rhubarb, and sunflower are all examples of the palmate venation seen in most dicots and eudicots.
Two or more equal veins start and end together at the leaf ends while running parallel to each other through the middle. Parallel venation is common to monocots, such as millet and other grasses.
Dichotomous venation is seen as repeated forking or Y-branching, as seen in Ginkgo biloba leaves.
Other venation patterns
You may also run into a few other leaf vein arrangements that don’t conveniently fall into one of those four groups. For example:
When you are trying to identify an unknown plant, venation can help solve the mystery!
Ferns look lovely in a stumpery, but there is surprisingly more to ferns that you might expect
These plants have been around for over 350 million years, long before flowering plants, or angiosperms, made their appearance. Or dinosaurs, for that matter! Ferns are vascular plants that do not produce flowers or seeds. Instead, they reproduce using spores, similar to mushrooms and other fungi.
There are over 10,000 known fern species of fern [so far] and some species can live for 100 years. While some ferns are nearly microscopic, others can reach 80 feet in height.
There is a group of ferns (Azolla) found predominantly in water and they do not look like any ferns you might see on land. One in particular, the mosquito fern, is able to fix atmospheric nitrogen the same way land-dwelling legumes do before going to seed.
Ferns have three basic parts: rhizome, fronds, and sporangia. Fern rhizomes come in three forms: erect, lateral, and vertical. Erect rhizomes provide the solid base from which leafy fronds unfurl. Laterally growing, creeping rhizomes move above and below ground and may even climb trees. Vertical rhizomes often look more like the trunk of a tree.
Fronds are a fern’s leaves. The leaf stem, called a petiole when referring to other types of plants, is called a fern’s stipe. The flat blade of the frond is called a lamina. The lamina is often segmented into pinnae by short stems called rachides. When a frond first appears, it is tightly curled and called a fiddlehead or koru. Fronds perform photosynthesis and they provide support for a fern’s reproductive sporangia.
Black, brown, or orange sporangia are the reproductive structures of ferns. If there are no sporangia present, the fern is sterile. Normally found on the underside of the fronds, spores are formed in the sporangia. A cluster of sporangia is called a sorus. In some cases, a flap of tissue, called the indusium, may cover the sori until the spores are mature.
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.
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:
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 greying, 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!
Heartwood is the dead center of a tree. It is usually a different color from the living wood and it provides the support needed to hold up a tree that might weigh several tons
Tree trunks are made up of several layers of tubes, surrounded by an outer layer of bark. These tubes are the vascular bundles that carry water and nutrients to the rest of the tree. One type of tube, called the xylem (or sapwood), pulls water and nutrients up from the roots. The majority of the trunk is made up of xylem cells. Another type of tube, called the phloem (or inner bark) carries the sugars made by the leaves through photosynthesis down into the rest of the tree. [I remember these two by saying, “Food flows down the phloem, while water and food rise in the xylem.”]
Just between the xylem and the phloem is the cambium layer. This is where the actual tree growth occurs. At the very center of the tree is the pith, surrounded by layers of xylem cells. As these xylem cells age, they eventually go through chemical changes that make them solid, losing their ability to transport water and nutrients. There is debate about whether or not these cells are still alive. This is the heartwood.
Characteristics of heartwood
Heartwood is very strong. The amount of heartwood present depends on the species. Some trees, such as ash, maple, and pine, have very thick heartwood. Other species have only a little heartwood. This group includes chestnut, mulberry and sassafras trees. Some tree species have no heartwood at all.
Heartwood gets larger over time. Young trees have very little heartwood, whereas older trees have significantly more.
Heartwood is resistant to decay, but wood that looks like heartwood might also be infected with disease or dealing with an insect invasion. Louisiana homes built over 100 years ago out of of bald cypress heartwood appear to be as good as new because of the decay resistance of heartwood.
The next time you need to remove a large branch or tree trunk, take a closer look at the layers and see if heartwood is present.
If you have ever canned jelly or fruit preserves, you have probably used pectin. Pectin is found in many plants and it has some unique properties.
The word pectin comes to us from the Greek word for “congealed” and with good reason. Pectin converts liquids into jelly, much the way gelatin does, the difference being that gelatin is made from animal skin and bones, and pectin is made from plants.
Pectin is found in most fruits, to one degree or another:
But fruits are not the only plants that contain pectin. Carrots hold an average 1.4% pectin. Commercially, most pectin is made from citrus peels and apple pulp. Soft fruits, such as grapes and strawberries also contain pectin, but at very low levels.
How do plants use pectin?
Pectin is a structural chain of molecules used in cell walls. Pectin is a major component of cellulose, specifically a layer called the middle lamella. The middle lamella is an outer layer to plant cells that is used to bind cells together. This allows plants to grow larger. The level of pectin present in a plant varies over time due to factors such as plant age and seasonal changes.
As fruits ripen, the pectin begins to break down, which is why the fruit becomes softer. A similar process occurs during abscission, when parts such as leaves naturally die and fall from the plant. In some desert plants, pectin has been shown to help repair DNA by creating a mucous layer that captures dew.
How do we use pectin?
Pectin is used for more than jelly making. Pectin also provides dietary fiber and it acts as a thickening agent and stabilizer for desserts, cosmetics, and medicines. Pectin also binds to cholesterol and slows the rate at which we absorb glucose. This is especially true when the pectin is from apples and oranges. You know that old saying about an apple a day? I guess they were right!
The pectin found in apple pulp is also one of the best throat lozenges I know. The mucilaginous pectin provides a surprising amount of soothing relief. Next time your have a sore or scratchy throat, skip the menthol (an irritant) and slowly eat an apple.
Molybdenum (Mo) is a plant micronutrient. So little is used that they used to be called trace minerals, but that doesn’t mean they are not important. Molybdenum is very important to your plants’ health.
Generally speaking, molybdenum is plentiful in alkaline soils and tends to be deficient in acidic soils. You can’t know what your soil contains without a soil test from a reputable lab. Those cute, colorful kits from the garden center don’t even test for molybdenum. Even if they did, they are not [yet] accurate enough to be useful.
How plants use molybdenum
Molybdenum is an essential ingredient to some very important enzymes. These enzymes are used in nitrogen, oxygen, and sulfur cycles. Specifically, molybdenum is used convert nitrate into nitrite and then into ammonia in order to be used to synthesize amino acids. It is also used by the bacteria responsible for converting atmospheric nitrogen into forms usable by plants. Molybdenum is also part of the process that converts inorganic phosphates into organic ones. Cruciferous plants, such as broccoli and cauliflower, and legumes, such as soybeans and clover, and citrus use a lot of molybdenum.
Plant nutrients are either mobile or immobile within a plant. Molybdenum is mobile, which means it moves around easily within a plant. This makes diagnosing deficiencies easier because they are most often seen in older leaves as plants pull nutrients to make new leaves. Molybdenum toxicity is practically unheard of, but deficiencies can be a serious problem.
Symptoms of molybdenum deficiency
Without molybdenum, leaves turn yellow and die and flowers may fail to form at all. The yellowing is often along leaf margins and downward cupping may also appear. In some cases, leaves develop a whiptail shape, rather than the leaf’s normal wider blade shape. Corn kernels may germinate on the cob prematurely in a last-ditch effort at reproduction. Legumes will have fewer or no root nodules if molybdenum is in short supply.
Again, you don’t know what your plants have access to without an inexpensive, lab-based soil test. Take my word for it, it is worth the effort.
Cabbage and mustard plants are probably not your first thought when it comes to fruit.
As strange as it may seem, the seeds and seed pods of radishes, broccoli, cauliflower, mustards, and other members of the cabbage family produce long, narrow, pod-shaped fruits called silique [se-LEEK]. If you only have one, it is called a siliqua [sil-eh-KWA].
More to pods than peas
Pods are a type of fruit that can be dehiscent or indehiscent. Dehiscent means that the structure opens spontaneously when its contents are mature. If a pod does not open automatically, it is called indehiscent. In either case, pods are made up of two identical long halves and they contain seeds. Those halves are called valves. Valves are the outer walls of the ovary. The two halves are joined along a seam, called a suture. Held between those two halves is a ribbon of seed-bearing tissue called the septum.
Siliquose fruit anatomy
If allowed to bolt, or go to seed, members of the cabbage family produce long, skinny fruits, commonly referred to as seed capsules or seed pods. These pods are each made from two fused carpels. The pods of legumes, such as peas and beans, are made from a single carpel.
If a seed capsule is more than three times as long as it is wide, it is called a silique, or siliqua. If a seed capsule is less than three times longer than wide, it is called silicle or silicula.
If you allow your radishes and other Brassicas to go to seed, you will see siliquae for yourself, plus you will have seeds for next year’s crop.
Now you know.
You can grow a surprising amount of food in your own yard. Ask me how!
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