Garden Word of the Day
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Boron isn’t nearly as boring as it sounds, once you know what it does for your plants.
Members of the cabbage family use a lot of boron, while peas and beans, peppers, and sweet potatoes need very little. Before you start adding boron to your garden soil, let’s take a closer look at what this element does for and to our plants.
Boron (B) is a micronutrient. In the world of plant food, micronutrients are only used in tiny amounts, but they are very important to plant growth. The optimal range for boron found in a soil sample is 0.1-0.5 parts per million (ppm). The only way you can determine how much boron is in your soil is with a laboratory soil test. Take my word for it, it’s the best investment you can make in your garden, next to mulching. But back to boron.
How do plants use boron?
Boron is critical for cell wall development and function, making those cell walls both strong and porous. The plasma membrane that allows molecules of sugar, water, wastes, and gases to move in and out of a cell rely heavily on boron to function properly. Research has also shown that boron is used by plants to produce and transport sugars within the plant, in protein synthesis, seed and pollen grain development, pollen tube growth, and flower growth and retention. Boron also plays important roles in nitrogen metabolism and fixation, the accumulation of the chemicals that affect taste (phenols), and in root development.
Boron, is most easily absorbed when soil pH is 5.5 to 7.5. First absorbed through root cells, boron then moves into the xylem, where it is taken to new leaves and shoots, or into the phloem, where it is taken to reproductive tissues, as well as vegetative tissues. Once boron is absorbed by a plant, it stays where it was placed. This is because boron is not a mobile plant nutrient. This is useful information because it means boron deficiencies will tend to show up in new growth before being seen in older leaves.
Helping plants get the boron they need
Boron is commonly leached out of the soil, leading to deficiencies, in areas with heavy rainfall. In drought-prone regions with very little rainfall, boron can build up in the soil, leading to potential toxicities. This is especially true for alkaline soil, or when too much fertilizer has been applied. [Just because a plant looks unhealthy does not mean it needs more food.]
Nutrient imbalances can make it difficult for a plant to absorb the nutrients it needs, even when those nutrients are present in the soil. For example, too much potassium in the soil can interfere with a plant’s ability to absorb boron, along with several other important nutrients. [The optimal range for potassium is 100-160 ppm.] Calcium and boron ratios are also very important to plant health. We will take a closer look at a tool, called Mulder’s Chart, that shows how these interactions work, in my next post. For now, we will look at what too little or too much boron can do.
Boron toxicity occurs when boron levels are at or above 1.8 ppm. Too much boron negatively impacts plant metabolism, and it reduces root and shoot development, chlorophyll production, rates of photosynthesis, and the lignin and suberin needed for structure and protection.
Toxic levels of boron can often be identified by looking at plant leaves. Too much boron will appear as either necrosis (death) or chlorosis (yellowing) of leaf tips and edges (margins). These damaged areas are believed to occur because the overabundance of boron interferes with several life processes, all at the same time. Unfortunately, these are the same symptoms as caused by magnesium deficiencies. [Can you say laboratory soil test?]
Adding extra boron is easy, when more is needed. Getting rid of excess boron requires more effort in the form of improved drainage through the addition of more organic material. Obviously, this takes time.
Insufficient or unavailable boron in the soil is the world’s most widespread micronutrient deficiency. It is a common problem in soils with low levels of organic matter (<1.5%). Boron deficiencies lead to reduced crop size and quality but symptoms can vary, depending on the crop:
Too much, too little, or no way for plants to get to the boron they need can all cause problems. Getting a laboratory soil test is the only way to know what’s eating your plants, or rather, what your plants are eating.
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?
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.
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.
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.
Yeast may help bread rise, beer froth, and wine ferment, but what does it do in the garden?
Is yeast a plant? An animal? Actually, yeast is a one-celled, sugar-eating fungus that urinates alcohol and farts carbon dioxide. It is those farts that make bread rise, and the other excretion that puts alcohol into beer and wine.
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.
Beneficial yeasts in the garden
Yeasts are not all bad. When it comes to protecting your strawberries, cherries, and cane fruits from the invasive spotted wing drosophila, torula yeast is used to lure this pest to its death. Also, recent research has demonstrated that adding brewers yeast to the garden may help plants counteract the effects of toxins in the soil. In another amazing study, it was found that a yeast found on the bodies of pollinating bees gets knocked onto flowers, as bees move around. Those yeasts then feed on the sugars in the flowers’ nectar. Breaking down those sugars generates heat, which keeps the flowers and the surrounding air space (used by the bees) warmer. This helps both parties survive winter. Yeasts also play a role in soil aggregate formation, improving soil structure. While other yeasts are believed to be part of the sulfur and nitrogen cycles, and make insoluble phosphates available to plants. Yeasts are food for many bacteria, insects, and other soil predators.
If nothing else, adding yeast to the compost pile will speed decomposition, assuming moisture and temperature levels are appropriate.
Did you know that some yeast species produce toxins that kill off other yeast species?
Now you know.
What looks like a light dusting of snow may actually be life-threatening pests, called adelgids.
Like their cousins, the aphids, adelgids pierce vascular bundles to suck out nutrient rich fluids. While mature, healthy trees can withstand a mild adelgid infestation, saplings, young trees, and unhealthy trees can be killed by this tiny, soft-bodied pest.
Scientists are still trying to nail down adelgid classification. There are 50 known species, all of which are native to the northern hemisphere, though several invasive species have made their way into the southern hemisphere. The most commonly found adelgids in California include the invasive balsam wooly adelgid (from Europe), the Cooley spruce gall adelgid (Adelges cooleyi Gillette), and pine adelgids.
Adelgids are commonly found on stone pine and other conifer species, such as pine and spruce. Depending on the host plant, the pests are commonly known as “pine aphids” or “spruce aphids”, respectively, even though they are not actually aphids. [Thanks to my friend, Chuck, I now know that adelgids are also found on apple trees. Thanks, Chuck!]
Aphids vs. adelgids
Aphids are significantly larger than adelgids, and they have two structures that adelgids do not: cornicles, and a tail-like cauda. Cornicles are tubes found sticking out of the 5th or 6th abdominal segments. These tubes are used to excrete a defensive chemical wax. Contrary to popular belief, cornicles are not used in honeydew distribution. Adelgids are covered with a dense wooly wax, so it is easy to mistake them for wooly aphids. This white fluff may be found on twigs, needles, bark, or cones.
Unlike aphids, which reproduce using both eggs and live birth, adelgids only lay eggs. Adelgids generally live for two years and each female can lay from one to several hundred eggs, depending on the species. Adelgid nymphs are called sistentes, which comes from a Latin that means ‘to stand’. When these sistentes overwinter, they are called neosistens. Some adelgid species require six generations to complete their lifecycle, moving between different tree species. Much like the Monarch butterfly, these insect pests do not live long enough to complete migration as individuals. Generally, it is only the immature stage that causes damage.
Damage caused by adelgids
Heavy infestations can cause yellowing, drooping, and dieback of twig tips. As they feed, adelgids release toxins that interfere with the tree’s ability to produce conductive sapwood. Eventually, the tree suffers severe water-stress and dies. These infestations can appear as swollen twigs, galls, or twig dieback. Adelgid galls look like tiny pineapples and can be green, red, or purple. The initial damage is usually seen on the underside of buds, before infestation and damage spread to the entire bud.
These pests are easily dislodged with a stream of water from your garden hose, but that only works you see them, which means you have to go outside and look. Beneficial predators, such as lady beetles, green lacewings, and some fly larvae. Horticultural oils can slo be used, but they will discolor spruce tree needles.
Infested twigs can be pruned out while they are still green (before adelgids have emerged) and thrown in the trash. Also avoid applying excess nitrogen, which can stimulate vulnerable new growth.
The National Park Service estimates that adelgids are responsible for the death of 90% of the mature fir trees found in the Great Smokey Mountains National Park, since this pest’s arrival in 1962. If you have conifers on your property, it is a good idea to inspect them periodically for signs of adelgid infestation.
Potato tuberworms are a minor to moderate pest, but they can make your potatoes inedible.
Also known as the potato tuber moth or tobacco splitworm, potato tuberworms (Phthorimaea operculella) love to feed on members of the nightshade family, such as eggplants, tomatoes, peppers, and tobacco, but they prefer potatoes.
The potato tuber moth is unique in the moth world in that her ovipositor (egg-laying organ) has sensors that can pick up chemical signals given off by potato plants. [If you are really into this sort of thing, the chemical signal is an amino acid called L-glutamic acid. But don’t worry, there won’t be a quiz.] She doesn’t necessarily have to be on the potato plant to lay her eggs, either, but you can be sure she will be close. These moths are usually seen an hour or two after sunset.
Potato tuberworm description
Potato tuberworms are the larval form of a small grayish-brown moth. The adult moth has a 1/2-inch wingspan and dark gray or black markings. At rest, both sets of fringed wings are held close to the body, giving them a slender appearance. Females moths have a distinctive “X” pattern on their forewings when at rest.
Eggs are very tiny, oval, and yellowish white. The larvae, or caterpillars, are just under 1/2 an inch in length, and their color can vary, depending on what they are eating, from white or gray, to tan, pink, or yellowish. Larvae have a brown head and prothoracic shield. [A prothoracic shield is the segment just behind the head.] Cocoons are 1/2 an inch long and pale colored.
Potato tuberworm lifecycle
Each female potato tuber moth will lay over 200 eggs in her short lifetime. Those eggs are normally laid next to a leaf vein, near a bud, or under a stem, though they can also be found in the soil near a host plant. In five days, those eggs will hatch. For the next two weeks, the larvae will eat as much as they can. The way they decide where to feed may surprise you. This is not a simple case of taking bites out of whatever is at hand. Nay, nay! Our newly hatched potato tuberworm larva will spend the first 5 to 15 minutes of its life walking around on its home plant. As it walks, it attaches a silk thread to the plant every few steps, turning this way and that way, taking an occasional bite as it meanders. If it has hatched on an unacceptable plant, the larva will walk faster and ultimately leave the plant altogether, until it can find an acceptable host plant.
Damage caused by potato tuberworms
Young potato tuberworm larvae might burrow through leaves and stems, causing stunting and reduced crop size. As feeding and tunneling continue, the tuberworms head for their favorite food: your potatoes. Webbing and frass (bug poop) deposits can be seen at entry holes, normally found at the eyes of a potato. While other pesky tunneling insects, such as wireworms and leaf miners, tend to keep their tunnels neat and tidy, potato tuberworms are slobs. Those dark tunnels are filled with excrement.
Controlling potato tuberworms
Row covers can be used to prevent adult moths from laying eggs on your potato plants. The deeper your potatoes are growing, the more difficult it is for tuberworms to get to them, so selecting a deep growing variety is helpful if you know tuberworms are around. Also, avoid furrow irrigation, which can cause cracks in the soil. These cracks are used as elevators to lower soil levels by tuberworms. Research has shown that insecticides do not prevent potato tuberworm infestations when erosion or soil cracks are present, or when potatoes are left in the ground longer than is necessary. Finally, harvest potatoes as soon as they are ready. Infested potatoes should be thrown in the trash and not added to the compost pile. Heavy infestations can be treated with spinosad.
Scabby potatoes? Yuck!
What causes this condition, and how can it be prevented?
First classified as a fungal disease, we now know that potato scab is a bacterial disease caused by Streptomyces scabies. There are other strains of Streptomyces that cause other potato diseases. S. scabies is found in the soil pretty much any place potatoes are grown. This bacterium can infect young seedlings of any plant, but it is most commonly associated with root and tuber crops, especially potatoes.
Delicious twice-baked and cut into wedges, served with sour cream and butter, potato skins are actually the cork, or periderm, layer normally found underneath bark. This layer normally provides protection from pests and disease. You may see tiny nicks of color in a potato’s skin. These are called lenticels and are used for respiration. This is also where the S. scabies bacterium gets in and starts infecting a potato.
Symptoms of potato scab
After entering a potato through a lenticel or wound site, S. scabies start setting up house. As they feed and reproduce, these bacteria release toxins into the surrounding plant tissue. The first sign of potato scab is nothing more than reddish-brown spots on the potato skin. These spots expand as the potato grows, becoming corky and necrotic. Then, the bacteria start reproducing (sporulating) in earnest, producing different types of lesions, depending on host resistance, time of infection, the aggressiveness of the bacterial strain, and other environmental conditions.
There are three basic types of lesions caused by potato scab: russet, erumpent, and pitted. Pitted lesions look like moon craters, while erumpent lesions are raised corky areas. Russet lesions (not to be confused with russet potatoes) are just extra corky tissue. In most cases, these lesions start out circular, but can spread out into larger, irregularly shaped areas. Potato scab lesions look a lot like another potato disease, called powdery scab. Powdery scab is a fungal disease caused by Spongospora subterranea.
How to prevent potato scab
Being a seed and soil borne bacteria, potato scab is best prevented by manipulating soil moisture, soil texture, and soil pH, and planting healthy stock You won’t get rid of the bacteria completely, but you can significantly reduce their numbers with these tips:
You can still eat potatoes infected with potato scab, but you should probably cut out the lesions and toss them in the trash.
Cousin to aphids and leafhoppers, potato psyllids can be a real pain, and not just for potatoes.
Potato psyllids (Bactericera cockerelli) are disease-carrying, life-sucking plant lice. These invasive pests also feed on tomatoes and other members of the nightshade family, along with several other garden plants.
Potato psyllid description
Potato psyllids are tiny. When I say tiny, I mean that an adult potato psyllid could stretch out comfortably across the edge of an American nickel, without dangling. If you get close enough, preferably with a hand lens or magnifying glass, you would see that they look like miniature cicadas. Potato psyllid adults are black, with a white band across the first abdominal segment and an inverted “V” on the final segment. They have clear wings that are held roof-like over the body when not flying or jumping. [They jump a lot.]
Potato psyllid lifecycle
Potato psyllids start out as eggs. Each female lays approximately 200 eggs, each of which hatches in 6 to 10 days. Those eggs look like microscopic footballs held to the underside of leaves with short stalks. [Do not mistake those short-stalked eggs to the longer stalked, beneficial lacewing eggs.]
After those eggs hatch into green, fringed nymphs, they look more like whiteflies or soft scale insects. Then, they go through five developmental stages, also known as molts or instars. Under ideal conditions, all that growing can be completed in less than two weeks.
Damage caused by potato psyllids
If sucking nutrient rich plant fluids wasn’t problem enough, potato psyllids cause other problems, too. For one thing, as nymphs feed, they release a toxin that can kill young transplants. This toxin also causes upward curling of leaflets closest to the stem on the upper portions of the plant. This condition is known as “psyllid yellows” or “vein greening”. The characteristic yellowing usually starts along leaf margins and then moves inward, turning purple in some cases. As this condition worsens, nodes [bumps where leaves emerge] become enlarged and closer together, rosetted clusters of leaves emerge from axillary (or lateral) buds, and aerial tubers begin to form. Aerial tubers grow at the end of aboveground stems, as opposed to underground stems, the way proper potatoes grow. When this pest feeds on tomato plants, it can cause no fruit production or overproduction of poor quality fruits.
Eventually, the once green, bushy potato plant looks more like a pitiful yellow Christmas tree. [If chlorosis is spotty and leaf rosetting is not present, the problem is more likely to be calico virus.] If potato psyllids are removed from the plant, the condition will stop progressing.
Potato psyllids are also carriers of another condition, known as zebra chip. Zebra chip is a bacterial disease that causes potatoes to store sugar, rather than starch. That might sound like a great idea for a new dessert food, but the presence of sugars cause ugly brown lines across the length of the potato. When cooked, these brown lines turn black, hence the name. This condition reduces crop size by 20 to 50%. Healthy appearing potatoes from plants affected by zebra chip are more likely to sprout while in storage.
Managing potato psyllids
You can’t control potato psyllids if you don’t know where they are. The first step to managing potato psyllids is to use yellow sticky traps. You can buy these at any garden center, or you can make your own with some yellow paperboard and sticky barrier goo. You should also inspect the undersides of leaves, looking for nymphs. While you’re at it, you should probably check the underside of any nearby bean or pepper plants, as these may also become infested.
In commercially grown potato fields, where potato psyllid is known to occur, a type of systemic neonicotinoid neurotoxin, called imidacloprid, is applied. [While not yet noted in California, resistance to imidacloprid has been documented in Texas.] Organic growers, like myself, use spinosad.
Because potato psyllids are not native to California, our local team of predators, which include lady beetles, lacewing larvae, and minute pirate bugs, have not been very effective at controlling this pest. Not yet, anyway.
Aphids on potatoes? Well, why not? They’re on everything else!
Potatoes are susceptible to two different types of aphids: green peach aphids and potato aphids. Today, we will learn about potato aphids.
Originally from North America, these pests are now found everywhere potatoes are grown. And potatoes are not their only food of choice. Your cabbages, tomatoes, eggplant, peaches, and peppers are also at risk, along with many other food crops.
Potato aphid description
Potato aphids (Macrosiphum euphorbiae) can be either green or pink, with a dark dorsal stripe, and they tend to be larger, with longer legs, than most other aphid species. When feeding on tomatoes, potato aphids become distinctly red. They have the same long-legged, soft, pear-shaped wingless body of other aphids. As populations boom, or food becomes otherwise scarce, some aphids will develop wings with which to fly to new feeding grounds.
Potato aphid lifecycle
Potato aphids, like other aphids, are phenomenally prolific. A single female aphid can produce 600 billion descendants in a single season. Aphids reproduce both sexually and asexually. When females produce offspring without male intervention (parthenogenesis), the offspring are born live and significantly smaller than their co-authored siblings. When reproduction involves a male counterpart, offspring are laid as eggs that overwinter in nearby weeds, or on other host plants. Adult aphids molt four times, leaving behind telltale white skins.
Damage caused by potato aphids
Aphid feeding is usually first seen as deformed leaves. As aphids feed, they damage plant tissue and disrupt the balance of growth hormones. This can reduce or eliminate crop size, and it can kill young plants. These sap sucking pests tend to cluster together, piercing plant tissue and sucking out nutrient rich fluids. They also poop out sugary honeydew, which attracts protective, disease-carrying ants, and creates habitat for sooty mold.
Potato aphid feeding can certainly weaken plants, but the real problem is that these aphids carry and transmit a number of viral diseases, such as cucumber mosaic, lettuce mosaic, bearded iris mosaic, narcissus yellow stripe virus, tulip breaking virus, potato virus Y, beet mild yellowing virus, beet yellows virus, alfalfa mosaic, and potato leafroll disease. Plants infected with potato leafroll disease will produce potatoes with a network of browning phloem tissue, called net necrosis, that is very unappetizing. Once a potato plant is infected with leafroll, it and three plants in all directions should be removed to prevent further spread of the disease.
Controlling potato aphids
The battle against aphids in the garden never ends. It starts by monitoring plants regularly for signs of infestation. Potato aphids tend to prefer the lower portions of plants, the undersides of leaves, and around new buds. You can dislodge aphids with a powerful stream of water from the garden hose, but it is practically impossible to get every single aphid off your potato plants in this way, and it only takes one aphid to start the whole process over again. Insecticidal soaps can be used with better results, but you have to make sure you wet every surface of the plant. Personally, I wipe them off whenever I see them. I like to think it slows them down a little, if nothing else.
The next step in controlling potato aphids is to remove nearby plants that might harbor these pests. This means keeping weeds away from potato patch. Malva, penny cress, and various mustards, in particular, can act as early season host plants for this pest.
Luckily, lady beetles, lacewings, syrphid or hoverfly larvae, and parasitic wasps will all help control potato aphid populations. That’s assuming you haven’t used broad spectrum pesticides and wiped out your helpers.
What's eating your potatoes?
From 1845 through 1852, over one million residents of Ireland starved to death, and another two million were forced to emigrate elsewhere, all because of potato blight. Before you lose your crop to potato blight, let’s learn more about this tiny water mold.
In the world of scientific classification, water molds are a type of mostly land dwelling organisms called oomycetes. Oomycetes fall between fungi and algae. These pathogens attack stems, roots, and tubers, and frequently kill host plants. Common water mold diseases include phytophthora tentaculata, crown rot, damping off disease, sudden oak death, and potato blight. Potato blight, also known as late blight, is caused by a specific oomycete called Phytophthora infestans. The word phytophthora means ‘plant killer’, and rightfully so.
The Great Potato Famine
The pathogen responsible for potato blight was first identified in 1843, in New York and Philadelphia. Wind then spread the spores throughout neighboring regions. Since potatoes weren’t found in North America until the 1500s, and then not grown regularly until the 1700s, potato blight wasn’t seen as a serious threat to anyone. Then, when seed potatoes were sent to Belgium in 1845, all hell broke loose for potato farmers across Europe. Ireland was hit the hardest in what became known as the Great Famine, or the Great Starvation. Since monoculture of a single potato species was common practice at the time, it wasn’t difficult for this disease to take hold.
Potato blight lifecycle
The potato blight pathogen prefers cool, moist environments, which Ireland has in abundance. Spores are produced 54°F to 65°F, while lesions develop when temperatures are between 64°F and 75°F. And it takes surprisingly little moisture to create a water mold habitat. Morning dew on a leaf is all it takes, though more water is preferable. These pathogens can also attack other members of the nightshade family, such as tomatoes, though another disease, called early blight (Alternaria solani) is often the culprit on tomatoes.
Water mold reproduction is odd. [Remember, oomycetes fall somewhere between algae and fungi.] Water mold reproduction starts with an asexual phase during which branching structures, called hypha, grow, followed by spore development. Then, the receptacle where spores develop, called sporangia, begin to germinate, much the way pollen granules germinate in fertilization. Then, our tiny water mold grows more hypha, and the process continues. Sexual reproduction occurs when two mating types meet.
Symptoms of potato blight
Potato blight symptoms start out as small, dark green, irregularly shaped, water-soaked spots on leaves, stems, petioles, and tubers. These spots have a yellowish halo. These lesions expand rapidly when moisture is present, turning purplish brown. Grayish white fuzz can also be seen on the underside of leaves as spores develop.
A special group of genetically modified potatoes has been developed with a resistance to potato blight. These cisgenic potatoes appear unable to catch the disease. If you prefer not growing genetically modified plants, there are other ways to prevent potato blight from taking hold.
How to prevent potato blight
Fixed copper sprays are the best preventative measures against potato blight. In fact, during WWII, when copper was being used to make artillery shells, farmers faced new threats from potato blight because they were unable to spray their fields.
Potato blight can find its way into your potato bed through contaminated potatoes, visitors and materials which have come from areas infested with the pathogen, and by rain or irrigation water splashing from contaminated plants to healthy plants. These are excellent reasons for quarantining new plants and avoiding the use of grocery store produce as a plant source. [Just because a plant is healthy enough to eat now does not mean it isn’t carrying diseases that may stay in your soil for years.]
Excess moisture should be avoided in areas susceptible to potato blight. This means allowing the soil to dry out between waterings, pruning for good air flow, and adding organic material to the soil to improve drainage.
A healthy potato bed is a thing of beauty. Let’s keep it that way!
Rain beetles only occur in California, Oregon, and southernmost Washington.
While they live here all year, rain beetles can only be seen after the year’s first big rain, or at spring’s first big snow melt. Even then, you will probably only see the males.
Rain beetle description
Rain beetles are scarabs, making them cousins to rose chafers, hoopla beetles, and Junebugs. Rain beetles (genus Pleocoma) are robust, shiny beetles. They are over one inch long, dark brown to reddish brown, with fuzzy undersides. [The word ‘Pleocoma’ is Greek for ‘abundant hair’.] That hair can range from black and brown to yellow.
Rain beetles have clubbed antennae with 11 segments, which is more than any other scarab beetle. Being filled with eggs, female rain beetles are much larger than the males. Once those eggs hatch, 3/4-inch long, C-shaped, creamy white larvae begin feeding and burrowing.
Damage caused by rain beetles
Adult rain beetles do not eat. They have no functional mouths or digestive systems, so they do not cause any damage to the garden. Their larvae, however, are another story altogether. Rain beetle larvae feed on the roots of fruit, nut, and ornamental trees and shrubs, and grasses, along with fungi and other organic matter. Rain beetle larvae seem to prefer the roots of apple, pear, and other orchard trees.
Rain beetle behavior
Rain beetle larvae do not dig through the soil, per se. Instead, they move through it by eating it and pooping it out. Burrowing up to 3 inches each day, a rain beetle larva can be found anywhere in the top 8- to 10-feet of soil. Adult rain beetles use powerful legs and a V-shaped scoop found on top of their head to push their way through the soil.
Male rain beetles generally emerge at dusk, though they can be seen flying around in the day, especially if it is raining. Males fly low to the the ground, looking for mates. Male rain beetles are relatively good flyers, though they will bang into your windows at night, being attracted to lights and bodies of water. Flightless females stay in the ground, emitting a pheromone that attracts the males. This pheromone has a lemony scent that is so strong even people can smell it.
Rain beetle lifecycle
Rain beetles are long lived bugs. From egg, to larva, to pupa, to adult can take 12 years. [Most beetle species only live one year.] That being said, by the time you see a rain beetle, it is probably only hours or minutes from death. Male rain beetles only store enough energy as fat from their more youthful stages to fly for a couple of hours, looking for mates, before dying.
After mating, female rain beetles burrow a spiral-shaped tunnel, as much as 10-feet below the soil surface, laying 40 to 50 eggs as she goes. In 2 months, the eggs hatch and the larvae begin feeding.
Rain beetles were once found throughout California and Oregon. Now, they are generally only found in pockets of foothill and mountain habitats. Being flightless and ground dwelling, female rain beetles have been wiped out everywhere urban development has occurred.
Rain beetle controls
Since rain beetles spend nearly all of their lives underground, chemical controls are ineffective. For the most part, rain beetles are more of a nuisance than a significant pest, though you can catch males in a butterfly net, if they really bother you.
Overwatering is the most common cause of death for houseplants and holiday plants. Under-watering can be just as devastating, indoors or out. So, how much water is enough, and how much is too much? And how can you tell?
Moisture meters measure the amount of available water in a soil sample. You can buy a simple moisture meter at any garden supply store. You can also install a multi-million dollar moisture sensing system throughout your landscape, but that’s beyond the scope of this blog (and my budget).
The trick to using a moisture meter is understanding the reading, and using the information properly to avoid water-stress. Before we learn how to read those results, let’s see what types of moisture meters are available.
Types of moisture meters
Handheld moisture meters measure soil moisture using a bimetal tip that measure electric conductivity. Other types of moisture meters use a variety of methods to measure soil moisture and its availability to plant roots. These other tools include gypsum blocks, tensiometers, watermarks, and neutron probes. [A neutron probe is a radioactive tool used by professionals who have been trained and licensed. If you get your hands on one of these, please donate it to your local County Extension Office as soon as possible.] Moisture meters either measure the amount of water in a soil (content), or how tightly the soil holds that water (tension).
The most commonly available handheld moisture meters do not require any real understanding about soil moisture. You simply stick the probe(s) into the soil, look at the display, and water accordingly.
These inexpensive moisture meters are very useful tools, though the probes tend to corrode rather quickly. Since each type of soil has unique properties, it is important to be able to calibrate your moisture meter for your soil texture. Salt levels in soil can have a big impact on moisture meter readings. If your soil has high salt levels, you will need to take that into account, as well. Also, where you place your moisture meter probe has a big impact on the usefulness of the information.
If you want to know more about soil moisture, read on. Otherwise, skip to the bottom section on caring for your moisture meter.
Each soil has its own water holding capacity. For example, if you have sandy soil that is saturated with water, gravity will pull any excess water downward, away from plant roots. If you have clay soil, as we do here in San Jose, water may be present, but much of it will be unavailable to plant roots. This is because clay has many small spaces with which to hold tightly to water molecules. [Adding organic material to clay soil increases the availability of that water.] The extent to which soil holds onto water is called its soil moisture tension. Soil moisture tension is measured in centibars (cbar). Most plants perform best between 40 and 80 cbar:
The amount of moisture available to plant roots is called a soil’s plant available water. Plant available water (PAW) can be measured as a percentage of weight, a percentage of volume, or by depth, as inches of water per foot of soil. Soil moisture content varies widely between different soil types:
When plant roots are unable to pull water from a soil, it will have reached its wilting point. The permanent wilting point occurs at 15 to 20% for clay soil, 10 to 15% in loamy soil, and at 5 to 10% in sandy soil.
How much water do plants need?
There is no correct answer to that question. [Sorry.] There are simply too many variables at play: plant type, age, size, and developmental stage, soil structure, soil texture, sun exposure, microclimate, time of year, air temperatures, recent weather… You get the idea. In California, UC Davis recommends one inch of water each week during the peak of summer. To fill a one foot by one foot area with water to a depth of 1 inch uses 0.623 gallons. In winter, your plants may not need any water, assuming it rains.
A plant’s need for water varies throughout its lifecycle. The biggest demand for water occurs during vegetative growth and initial fruit production.
Since this normally occurs during summer, when evaporation is at its peak, maintaining the proper moisture level makes the difference between healthy, productive plants, and plants that are struggling for survival. As temperatures drop or senescence (preparation for death) begins, the need for water drops dramatically. Adding more than is needed creates a different sort of life-threatening set of conditions. [Can you say fungal disease?]
Caring for your moisture meter
The sensor found at the end of most moisture meter probes is sensitive to damage and corrosion. To keep your moisture meter operating properly, be sure to wipe it off after each use and do not force it into dry, compacted soil. If a reading is needed under those conditions, create a starter hole with a screwdriver. Also, watch out for rocks, which can damage the probe.
As an added benefit, many moisture meters can also provide you with soil pH information. This is one tool every gardener should have on hand and use regularly. Just remember, you get what you pay for.
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.
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!
Garden Water Features
There is something about garden water features that makes everything better.
Calming, refreshing, or splashing playfully, water has the ability to improve our mood, create art, and support local biodiversity. And, hey, it looks nice!
Benefits of water features
Water features provide many benefits other than the artistic appeal. Water features can provide life-sustaining moisture for hummingbirds, butterflies, other insects, reptiles, and amphibians, many of which are severely threatened these days with habitat loss. You can encourage honey bees and other pollinators to come to your garden when a water feature is present.
Water features can suit any style, from rustic to elegant, quirky to traditional. Water features also tend to improve curb appeal and property values, if you are thinking of selling your home. If you are even the least bit handy, you can install your own garden water feature. [Instructables has some excellent ideas!] You can get the necessary information from your local library, or you can buy a kit.
Types of garden water features
Water features come in all shapes and sizes. They can be birdbaths, fountains, or waterfalls, ponds or pools, or even a creek or stream. Starting with the most simple water feature, and moving through to more complex features, each has its own pros and cons.
A simple birdbath can often be found at yard sales and thrift stores. You can also make your own with a wide, shallow bowl, or any other container that has sloping sides. While a birdbath requires regular refilling and cleaning, it is very rewarding to see goldfinches, mourning doves, and jay birds drinking and bathing. Add a pump to a small water-holding container and you have a fountain, or a waterfall.
Fountains and waterfalls
Fountains and waterfalls are especially good at transforming a space without a huge expense. And you can now find solar pumps to power a garden water fountain. Fountains add water movement and oxygenation to your water feature. This slows the growth of algae and reduces the likelihood of creating a mosquito breeding ground. Also, the sound of falling water can be very soothing, and it can mask less desirable sounds of traffic or noisy neighbors. Moving water also adds moisture to and helps clean the surrounding air, supporting nearby plants and animals, along with your family. You will need to maintain water levels in your fountain, especially in summer. Also, fountains do need to be cleaned occasionally, to keep water flowing through the pump. If you have more room, a pool or pond might make a lovely addition to your garden.
Ponds and pools
While swimming pools have chemicals and steep sides that can prove detrimental to most local wildlife, small ponds and pools take up only a moderate amount of space and can often be self-sustaining. [And who wants the wildlife playing in your swimming pool, anyway?] A small pond can create a shady sanctuary for weary feet, brilliantly colored koi, and overheated dogs, along with local wildlife. You can take a pond idea one step further by using the soil dug out for the pond to create a sloping creek.
Creeks and streams
Backyard creeks and streams create a magical space in your yard. And these systems are mostly self-contained. Water is pumped from the pond, through a filter, and then up over a small waterfall. Because the water is moving, you get the sights and sounds of running water, the water is oxygenated, and the filtering system reduces the amount of maintenance you need to provide.
Ponds with creeks also create ideal habitat for shy amphibians and reptiles who will feed on pesky beetles, wasps, and other pests. You can find affordable kits that walk you through the installation, or you can hire a professional.
Garden water features add beauty and value to your home and garden, while improving the quality of life for all nearby living things.
Lenticels are porous tissues used in plant respiration.
Plant respiration involves exchanging oxygen, carbon dioxide, and water vapor as part of photosynthesis and other cellular functions to generate or release energy.
The words ‘lenticel’ and ‘lenticular’ refer to the more common lentil-shape of these openings, but theses raised areas can be round, oval, or elongated. In some cases, such as silver birch, lenticels appear as horizontal cracks.
There are two types of lenticels: those found in the stems, trunks, and roots of woody plants and trees, and those found in the skin of certain fruits, such as apples.
Many apples and pears, in particular, have fruit skin lenticels. These are the tiny nicks of color seen on the skin. These lenticels start out light colored and then darken as the fruit reaches maturity and is ripe for picking. This darkening occurs because of the formation of cork cells. These openings are often the site of failing stoma, broken off trichomes, or other points of early damage, rather than planned growth. The number of lenticels seen on pome fruits can vary by species and by the availability of water during early development.
Bacterial and fungal disease can enter the fruit through these openings. There is a global skin disorder of pome fruits, called ‘lenticel breakdown’, in which 1-8 mm pits develop at the lenticels just after processing.
Trees and other woody plants have lenticels in their bark (periderm), both above and below ground. These openings facilitate the necessary exchange of oxygen, carbon dioxide, and water vapor. Since different species have uniquely shaped lenticels, knowing the characteristic shape of a tree’s lenticels can help in identification
Trees growing in low oxygen environments, such as mangroves, have lenticels on specialized roots. Grapes, on the other hand, have lenticels on their pedicels, or flower stems. Grape lenticels react to changes in temperature, rather than oxygen levels.
Did you know that potatoes have lenticels?
Now you know.
Mammals in the Garden
Not counting gardeners, there are several types of mammals that may turn up in your garden. Some can be helpful, others can be a royal pain.
Mammals are warm-blooded and more or less intelligent. This can make excluding them from certain areas of the garden problematic. In most cases, there are ways to work around pesky mammals in the garden, without losing your mind or getting in trouble with local law enforcement.
Speaking of law enforcement, before you go trapping, shooting, poisoning, or otherwise dispatching wildlife, you need to track down your local laws and obey them. The low level squirrel feud can turn into a legal nightmare if improper methods are used against them. It’s not worth it - regardless of how tempting it may be when they take your last juicy pears for the umpteenth time!
So, let’s see which animals might end up in the garden and how to protect your plants against them.
There are three major types of bats found in North America: leaf-nosed bats, vesper bats, and free-tailed bats. These bats are primarily insectivores, capturing insect pests, such as moths, wasps, flies, mosquitoes, in flight, or capturing beetles, ants, and other insects off of leaves or from the ground. This makes bats welcome guests in the garden, though they will sometimes eat ripe fruit. [Who can blame them?] You can attract bats to your garden for the evening shift by installing a bat house.
Deer are the bane of gardeners wherever they are found. These animals can leap small buildings in a single bound. Oh, wait, wrong story. But deer can wipe out an orchard, garden, or landscape, between feeding and trampling, in short order. Really high fencing (and I mean 7- or 8-feet high) might block deer. If your garden is on a slope, you will need fencing that is 10- or 11-feet high! Loud, scaring devices and various repellants can also be used to try and block these determined garden pests, but the effectiveness of these methods doesn’t last very long.
In California, we have deer mice, house mice, and meadow mice, also known as voles. Deer mice and house mice are mostly seed eaters that can wipe out a garden crop before it even starts. Voles are herbivores that will eat your bulbs, tubers, artichoke, beets, Brussels sprouts, celery, cauliflower, sweet potatoes, lettuces, tomatoes, turnips, cabbages… well, you get the idea. If that weren’t enough, voles will also chew the bark off your fruit and nut trees.
While poisons do kill mice, those poisoned mice can then be eaten by other wildlife, or your pets, so I urge you to avoid poisons. And those sticky boards, well, those are just cruel. Also, as the animal struggles to escape the glue, they tend to urinate and defecate and those materials then get slung around as the animal continues to struggle. Instead, good old fashioned mouse traps are still your best bet. They are usually an instant death and generally not very messy. Since all mice can carry hantaviruses, be sure to wear non-fabric gloves whenever handling mice, materials mice may have urinated on, or mice droppings. Also, be sure to thoroughly disinfect any areas inhabited by mice.
Moles and shrews
Shrews and moles may look like mice with deformed noses, but they are not rodents. They are more closely related to hedgehogs. There are 13 shrew species and 4 moles species in California, and they spend most of their lives underground, digging burrows and eating. For their size, shrews have voracious appetites, eating 1/2 to 2 times their body weight each day in worms, insects, and other invertebrates. They will also eat seeds, roots, and bulbs, but mice and pocket gophers are usually the culprits in those cases. Trapping is the most effective control measure, though chemical repellants and noisy, scaring devices can provide some protection.
Opossums may look prehistoric, but they can do your garden a good service. While they will sometimes eat fresh fruit and vegetables, opossums much prefer rotting produce, ticks, slugs and snails. In my book, that makes them a beneficial visitor. If an occasional tomato is lost, well, it seems a fair price.
Pocket gophers spend most of their time underground, digging burrows that lead to many of your garden and ornamental plants. We have 5 gopher species in California and they all feed on roots from below. They will also grab a tasty plant and pull it below ground to enjoy in relative safety. In a single night, one pocket gopher can destroy an entire garden row. Gopher traps are your best control measure.
Rabbits, hares, and pikas
Contrary to popular belief, rabbits are not rodents. They are lagomorphs. There, I said it. Now, what are pikas? And what’s the difference between rabbits and hares? Well, rabbits are smaller than hares, and hares, also known as jackrabbits, have longer legs and ears. Also, hares change color with the seasons, while rabbits do not. As for pikas, you probably won’t ever see them because they tend to live at elevations above the tree line, but they are cute. So are rabbits and hares - until they decimate your salad garden or other crops. Keeping rabbits and hares out of the garden is an unending battle. Since they can burrow, fencing alone is not enough. Raised beds with an exclusionary hardware cloth base may be your only real solution if these pests are feeding on your garden.
Raccoons are smart. And when they are not attacking your chickens or eating your pet’s dinner, they are probably busy eating your garden fruits, berries, nuts, corn, or other grain. Raccoons are attracted to compost piles, trash cans, and bird feeders. Raccoons may also try using your house, chimney, or garage as a nesting site. While young raccoons are adorable, these nests mean the presence of urine, feces, and disease-carrying parasites. Also, unlike opossums, raccoons tend to carry several diseases, such as roundworm, distemper, and rabies. Raccoons are best controlled with live traps. As a furbearer, raccoon pelts have value, so you can probably find someone who will be happy to discharge a trapped raccoon. Otherwise, you can discretely relocate your visitor somewhere more appropriate, and less destructive. Just be sure to check on your legal obligations before you get yourself in trouble.
Wherever you live, you probably have rats. The two most common types of rats are Norway, or sewer, rats and roof rats. These pests are filthy, destructive, and difficult to get rid of. Rats carry diseases, chew through electrical wires, and can damage your home, along with your garden. Roof rats prefer avocados, berries, citrus, and nuts, while Norway rats prefer meat and grain. Before you protect your garden against these pests, be sure that there are no points of entry to your home. Once your house is secure, then you can start trapping outdoors in earnest.
There are spotted skunks and striped skunks. In either case, it is a good idea to stay at least 10 feet away from the back end of a distressed skunk. [By the way, skunks have terrible eyesight. If you find yourself closer than you would like, be very, very still, or move away very, very slowly. A startled skunk is an unpleasant experience.] Both skunk species will eat pretty much anything: garbage, compost, pet food, worms, fruit, berries, mushrooms, beetles and other insects, lizards, frogs, snakes, and even the occasional bird egg. Since skunks are the most common carrier of rabies in California, along with distemper, canine hepatitis, leptospirosis, and several other diseases, getting them out of your garden (or out from under your porch) is a good idea. This is best done by professionals. Very often, your local Animal Control Office will remove skunks for free. Once a skunk family is removed, it is important to block whatever area, or remove whatever feature, attracted them in the first place. Otherwise, you will just get a new skunk. If you are unfortunate enough to be bit by a skunk, see your doctor right away. Seriously.
There are two major types of squirrels: tree squirrels and ground squirrels. If I didn’t have dogs, I would probably have nothing to show for all my work in the garden because of squirrels. I was surprised to learn that they will eat oranges, tomatoes, blueberries, pears, and more. Adding insult to injury, squirrels will, like birds, often only take a bite or two before moving on to the next delectable piece of fruit, leaving a trail of potential disease behind them everywhere they go. Hardware cloth and chicken wire are the only reliable barriers to squirrel feeding, though I have had some success with a repellant called Bobbex-R.
Finally, our pets.
We love our pets. There’s no denying that cats and dogs have a very special place in our hearts. That being said, we do not want cat feces next to our lettuces, or dogs digging up rows of beans or tomatoes. As much as your cat may love being outdoors, researchers at UC Davis have demonstrated that your cat is perfectly happy and actually safer kept indoors. Being stealthy predators, cats can decimate local bird, reptile, and amphibian populations, and we need those other creatures more than your cat needs time outside. Dogs can be trained to provide several beneficial services in the garden. My two dogs will chase squirrels, raccoons, rats, mice, opossum, jays, and cabbageworm butterflies out of my garden. Since most of my gardening is now done in raised beds, I don’t have to worry about the dogs running through them.
While we need to learn how to live and let live, there is nothing wrong with protecting what is yours. This is especially true for disease carrying pests. In some cases, it is simply easier to fence in your crops with netting and tree cages. For those mammals in the garden that must be killed, please use the fastest, most painless method.
How do you manage mammals in your garden?
Amphibians in the Garden
Frogs, toads, newts and salamanders are all amphibians that you might find in your garden. If you are lucky.
Of course, luck has very little to do with creating a healthy environment. It takes fact based knowledge and a little effort. With just a few slight modifications to your garden, you can create a habitat that attracts these beneficial creatures and encourages them to stay. But why would you want to?
Benefits provided by amphibians
Newts (a type of salamander) are one of the few animals that love to eat slugs. For that reason alone, I am happy to create an amphibian-friendly habitat. Most amphibians are insectivores, which means they will reduce the number of snails, beetles, worms, millipedes, and whatever else they can catch and swallow. While still in their aquatic stage, amphibians will also eat mosquito larvae, along with other insect eggs, water snails, and even small fish.
What are amphibians?
Amphibians are cold-blooded, and many of them start out in water before moving to land. In fact, the word ‘amphibian’ comes to us from the Ancient Greek amphibious, which means ‘both kinds of life’. Amphibians evolved from fish approximately 370 million years ago.
Most of us are familiar with the way frog eggs hatch in water and are called tadpoles. Those tadpoles then lose their gills and tails to become adult frogs and toads. Baby salamanders and many other amphibians also start out in water. At this early stage, they are called larvae. Then, they generally go through some sort of metamorphosis to reach their adult size and shape, and to start breathe using lungs. [Did you know that amphibians also breathe through their skin? For some species, skin breathing is their only form of respiration.] Amphibians often have glands in their skin that release toxins, as a defense mechanism. For this reason, it is a good idea to not handle your garden amphibians - they probably wouldn’t like it anyway.
There are approximately 7,000 species and 3 orders of amphibians in the world: frogs and toads (Anura), salamanders (Urodela), and blindworms, or caecilians (Apoda).
Each region has its own native amphibian population. The first step to improving the biodiversity of your garden is to learn which amphibians are native to your area. Here in the Bay Area, we have a wide variety of amphibians, just looking for a home:
Frogs and toads
Salamanders and newts
How to attract amphibians
Most amphibians start out in or near water, so a pond or similar water feature is the best way to attract amphibians to your landscape. The water should be at least 20 inches deep, and provide both sunny and shady areas, with sloping edges. You will also want to incorporate floating, submerged, and plants that grow from the bottom of your pond to above its surface. The ideal ratio of plants to open water is 1:1. Unlike your swimming pool, you will want algae to grow in your pond, as it is an important food source and it generates oxygen for tadpoles and larvae.
If a pond is completely out of the question, you can still maintain a moist area that includes rotting logs and leaf litter. Brush and rock piles, a stone wall, and basking areas will also help lure these beneficial creatures to your landscape.
Incorporating native plants will attract other natives, providing both food and family for your amphibians. Under no circumstances should you release a nonnative amphibian into your garden. This is how ecological disasters often start.
Other ways you can help your local amphibians include allowing your lawn to grow a little taller, to provide safe travel corridors, reduce or eliminate your use of chemical pesticides, fertilizers, and snail pellets, keep your cat indoors, and monitor your dog. Also, be on the lookout for hidden amphibians when using a lawnmower or weedwacker.
Amphibians are very sensitive to toxins in the environment. This is why they are considered an indicator species. If you have amphibians in your garden, then you know you have created a healthy place. Similar to the recent decline in insect populations, amphibians are currently facing a mass extinction.
Recent studies tell us that, before the 1500s, the expected rate of amphibian extinction would be 1 to 11 species lost over a 500-year period. Since the 1500s, 35 to 130 species of amphibian have become extinct. Since 1980, 9 to 122 more amphibian species have become extinct, with an additional 1,896 species in “imminent danger of extinction”. [The numbers are ranges because it is very difficult to prove that a species is finally and irrevocably gone.]
While most mass extinctions span a couple of million years, the current mass extinctions can be measured in centuries and are caused, both directly and indirectly, by us. The current amphibian population crash is attributed to disease, habitat loss, introduced species, pollution, climate change, and pesticide use, though it is not completely understood. Nor do we understand the long term ramifications of this mass extinction.
The food web and network of life here on Earth is very complex. The loss of amphibians is bound to have serious implications for all of us. Please, do your part to make life possible for amphibians in your garden.
Reptiles in the Garden
Reptiles in the garden? Let’s hope so!
You may see a lizard scurrying for cover under your lettuces, or a snake slithering across your strawberry patch, but what are they doing in your garden? Are they pests or helpers? And what’s the difference between reptiles and amphibians?
Reptiles v. amphibians
Reptiles and amphibians are both cold-blooded. This does not mean that they are insensitive or cruel, it simply means that they cannot keep themselves warm. If you want to attract reptiles and amphibians to your garden, this is helpful information. The difference between reptiles and amphibians is seen in their skin. Reptiles have dry, scaly skin, while amphibians have smooth, moist skin. Also, amphibians start their lives in water, breathing through gills, while reptiles do not. The classification of reptiles and amphibians may surprise you…
Reptile and amphibian classification
Reptiles (Reptilia) include crocodiles, lizards, turtles, and, wait for it - birds! Before you lose your mind, hear me out. The classification system you grew up with, the Linnaean system, was developed in the 1730’s by Carolus Linnaeus. [I was allowed to pick up and read one of Linnaeus’ first edition copies of Systema naturae, sive regna tria naturae systematice proposita per classes, ordines, genera, & species (1735), during my visit to the Missouri Botanical Gardens!] Linnaeus’ work was based solely on physical characteristics, which meant birds and lizards were in two separate clades. [Clades are subdivisions of a class, descendants of a common ancestor.]
In the 1940’s, a biologist named Willi Hennig came up with a different classification system. His system is based on genetic ancestry, and it is called phylogenetics. Using this more accurate method, birds are members of the reptile class.
What are reptiles?
So what makes a reptile a reptile? First, all reptiles are descended from 4-legged, cold-blooded vertebrates. The reptile clan includes lizards, snakes, and turtles. Skinks are a type of lizard. Most reptiles hatch from eggs (oviparous), while some give live birth (viviparous). Reptiles can range in size from the tiny gecko, at just over 1/2 an inch in length, to the giant, 20-foot saltwater crocodile. Reptiles shed their skin as they grow, so you may find signs of a resident lizard, even if it is too shy to let you catch it out in the open.
What do reptiles eat?
Most reptiles are carnivores or insectivores, though there are a few exceptions. This is what makes [most of] them so useful in the garden. Local reptiles will feed on aphids, ants, beetles, flies, wasps, grasshoppers, slugs and snails, smaller reptiles, baby voles, mice, and rats, sowbugs, earwigs, and practically anything else they can grab, including beneficial spiders and worms, and even baby birds
Why attract reptiles to the garden?
Creating habitat for native reptiles in or near your garden is an easy way to limit pest populations without any chemicals or effort on your part. Just be sure that you do not release an invasive pet reptile into your yard - this is how ecological disasters often start. Please don’t do it. In California, native lizards may not be captured or sold, so you can’t buy them. What you can do is create a welcoming habitat. They will find it, sooner or later.
To attract reptiles, use these tips to provide healthy habitat for reptiles and their prey:
Nearly all reptiles found in California are harmless, with the exception of rattlesnakes, Mexican bearded lizards, gila monsters, and a handful of others. Since reptiles are mostly shy, conflicts are rare. Creating habitat for these elusive garden helpers is a great way to cut back on your work load, while increasing biodiversity in your garden.
Did you know that crocodiles are more closely related to birds than they are to lizards?
Now you know.
Pests, predators, and pollinators, whatever role they play in the garden, insects are everywhere. Or, are they?
Most of the world’s insects evolved in tandem with flowering plants (angiosperms). The majority of insects are small, but a few of those early insects were huge by today’s standards. Dragonflies, known as predatory griffinflies, had wingspans of over 2 feet, and cockroaches were the size of house cats. This was due, in part, to higher oxygen levels in the atmosphere. [31-35% oxygen then, 21% today - don’t panic, though, these levels have been fluctuating since Earth was formed.
Changing oxygen levels were not the only reason for some insects getting smaller. Research has demonstrated that the evolution of insect-eating birds, around 50 million years ago, also played a big role in this change. As bird (and bat) predators started feeding on insects, those prey animals had to become more mobile, harder to see, and less delicious to survive.
Today, insects are facing the biggest threat to their existence - us.
Recent studies show an alarming decrease in insect populations around the globe. Today, we will be learning about different types of insects, the benefits they provide, the problems they face, and ways we can help.
Insects are spineless, 6-legged, armor-plated creatures with three-part bodies, compound eyes, and antennae. To put those characteristics in more scientific terms, insects are invertebrate hexapods with a chitinous exoskeleton.
The word ‘insect’ comes to us from the Latin word insectum, which means ‘with a divided body’. An insect’s body consists of the head, thorax, and abdomen. The legs and wings attach to the thorax. Insects have two types of eyes: simple and compound. Simple eyes (ocelli) are a single lens that can see clearly. Most insects have three simple eyes on top of their head. Compound eyes are those bulging eyes we can easily see. Insects’ compound eyes can have dozens, hundreds, or even thousands of lenses, called facets.
Insects represent between 50 and 90% of all living things on Earth, with over one million named species, and an estimated 4 to 10 million unnamed species. Cousin to spiders and crustaceans, insects come in an astounding array of shapes, sizes, and colors.
A bug by any other name
All bugs are insects, but not all insects are bugs. The word ‘bug’ only refers to true bugs (Hemiptera). True bugs all share piercing, sucking mouthparts that may be used on plants or other insects. There are approximately 80,000 different types of true bugs worldwide, along with 12,000 ant species, 20,000 bee species, and 400,000 types of beetles.
Insects are first classified as winged (Pterygota) or wingless (Apterygota), though not all winged insects can fly. Winged insects are further classified by when and where those wings develop. True flies, bees, fleas, ants, beetles, and butterflies and moths go through a complete metamorphosis, with the wings developing inside the insect during a pupal stage. These insects are in the Endopterygota order. Insects whose wings develop outside of the body, as with dragonflies, lice, mantids, and earwigs, it is considered an incomplete metamorphosis and these insects are in the Exopterygota order.
Most insects hatch from eggs. Rigid exoskeletons are shed in a series of molts, as an insect grows. Some baby insects, such as praying mantis, look like miniature adults, while other insects, such as the Monarch butterfly, go through a complete, 4-stage metamorphosis that includes a pupal stage. While other insects have a 3-stage metamorphosis, in which there is no pupal stage, but a series of nymphal stages.
Pests, parasites and pollinators
Insects are profoundly important components of an environment. They aerate the soil, eat pests, pollinate one-third of all crops (by volume), feed local wildlife (and domestic chickens!), and recycle natural materials into forms usable by plants. Insects play a major role in the creation off topsoil. Insects are also eaten as food by 80% of the world’s nations. Insects can also carry disease, destroy crops, and damage buildings.
Initially, chemical insecticides were seen as the first line of defense against unwanted insects. Because many insects are able to develop a tolerance to those dangerous chemicals (and we cannot), other methods of control are being explored. Very often, beneficial insects, such as parasitic wasps, and other natural predators, such as birds, are encouraged or imported into an area to control harmful insects. These integrated pest management methods reduce our reliance on chemicals and increase local biodiversity.
Declining insect populations
We have been so focused on killing insects off that we didn’t notice, at first, when their populations started to decline, or by how much. Hard, verifiable population facts are still difficult to come by, but recent research has shown a 45% decline in invertebrate populations worldwide. Now, that figure includes more than just insects, but the news is alarming. One German entomological society has recorded nearly 80% less insect biomass in their studies. Another German study reported a 75% decrease in the total flying insect biomass over a 27 year study on 63 different sites. Now, biomass does not mean number of insects. It also does not tell us which type of insects. It simply tells us the amount of insects by weight. Also, not all sites were studied every year, so please do not take this study to say that ’75% of all insects disappeared over 27 years’, because that’s not what the study claims. What it does tell us is that this is a very real problem.
Declining insect populations are the result of many different factors:
The food web ties all living things together. As insect populations fall, so do bird, bat, fish, and amphibian populations. European ornithologists (bird experts) point to declining insect populations as a fundamental reason behind 80% less partridges and turtledove, and 50% less nightingales currently found in the French countryside. In the past 30 years, over half of all Europe’s farmland birds have disappeared, and we have to assume that similar results are occurring locally.
Call to arms
Scientists recognize the critical nature of insect population decline, and the lack of verifiable information. To counteract that lack, large-scale monitoring is being called for, using photos, videos, acoustic recordings, traps, genetic fingerprinting, and citizen science. Automated data collection, worldwide, is the only way we can learn where insects are and how their populations are behaving, and you can help, too.
How you can help insects
There are many things you can do to help insects at home:
Did you know that earwig mothers clean, protect, and keep their eggs warm?
Now you know.
Tree Planting Depth
Planting trees too deeply has become the Number One reason why trees fail.
Is your tree failing to thrive? Does it seem overly susceptible to fungal diseases and pests? Are leaves smaller, scorched, or otherwise discolored? Has seasonal leaf color change started occurring earlier? Are wilting, early leaf drop, or twig dieback been occurring? Are you seeing more water sprouts and suckers? Have you noticed less new twig development? It may be that your tree is planted at the incorrect depth. Even heavy fruit production can indicate a problem. Confused? Don’t be. Producing fruit is a tree’s way of continuing the species. If the tree is dying, it will put everything it has into ensuring a big crop of potential future generations.
A properly planted tree shows a flare at the base of the trunk. If your tree looks more like a fence post, it is probably planted too deeply. In the world of botany, a tree planted too deeply is said to be planted ‘below grade’. Trees with exposed roots were planted too shallowly and are ‘above grade’.
Knowing how to plant a tree at the proper depth (or how to correct the problem once it occurs) is the best way to keep your trees healthy and productive.
Start your trees better
When you first buy a young tree, it is usually in a container or the roots are balled up in a burlap bag. In both cases, the young tree has 5 to 20% less feeder roots than a similarly sized tree growing in the ground would have. As a result, these young trees dry out more easily and are easily stressed. If that weren’t problem enough, putting that stressed tree in the ground at the wrong depth can kill it, though it may take a few years. The goal of planting is to get your tree in the ground in such a way that new roots can grow quickly and properly.
Proper planting depth
The majority of a tree’s roots are in the top 18 to 24 inches of soil. They spread out horizontally and vertically from the center, well beyond the drip line, in their search for food, water, and air. [The drip line is the outer circumference of the tree canopy, where rain water drips to the ground.] To plant a tree at the proper depth, use these tips:
Ultimately, you want at least two structural roots to be in the top 1 to 3 inches of soil.
Planting too deeply
The roots closest to the surface are responsible for a large portion of a tree’s respiration. Tree respiration is not the same thing as human breathing. Tree respiration refers to the process by which a tree performs the gas exchange used to generate or release energy. If a tree is planted too far below grade, those surface roots will still grow horizontally and be unable to get at the air they need.
Planting too shallowly
The primary vertical roots of trees planted too shallowly (above grade) will not grow out into the air. They simply dry up and die. This reduces the water and nutrients available to the growing tree. These upper roots may also try growing into the mulch, where there is limited food and water, or they will simply go around in circles, becoming root bound in the planting hole. This is one way that girdling roots occur.
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.
You can grow a surprising amount of food in your own yard. Ask me how!
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