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Writing yesterday’s post on soil horizons, I ran across a couple of unfamiliar words. Marl was one of them. Here’s what I’ve learned about marl.  Marl (Tashkoskim) CC BY-SA 4.0 The word marl comes to us from the late 19th century. It is short for marbled. Rather than being as hard as your favorite cat’s eye or aggie marble, marl is a porous, relatively soft mudstone. And it contains many of the nutrients your plants love. The lower cliffs of Dover and much of New Jersey contain marl.  White Cliffs of Dover (Immanuel Giel) CC BY-SA 3.0 Marl formation Marl forms as carbonate-rich clay mud and silt are blended with algae that loves alkaline waters. The carbonate is from the dead shells of water-dwelling organisms and the calcified algae. Originally the term marl only referred to freshwater formations. We now know that marl occurs in saltwater too.  Coastal marl formation, southern Sicily (Carnby) CC BY 3.0 Types of marl Marl contains 65–35% carbonate and 35–65% clay, depending on the type. It can be blue, green, sand-colored, or red. Marl contains calcium, iron, phosphorus, potash, silicic acid, and sulfur. It also contains magnesium, but only a little. Magnesium deficiencies are common in fields treated with marl.
Soil is fundamental to the health and productivity of your plants. Healthy soil supports healthy plants. But there’s more to soil than meets the eye  Soil layers tend to get progressively lighter in color (Chris Yeates) CC BY-SA 2.0 You’ve heard a lot about topsoil and maybe some about bedrock, but what about the layers in between? The layers of soil under your feet have developed over eons of glaciation, erosion, flooding, and thousands of other circumstances of pedogenesis. Underneath it all is your soil’s foundation, or bedrock. Of course, if you go deep enough you’ll reach the molten core, but that only affects gardeners in places like Hawaii. For most of us, it is only the top few feet that dictate the health of our plants. There are several different layers and those layers are called horizons. There are different classes of thought on soil horizons. Some groups define these layers by the soil texture, while others prefer sorting them by use. Keep in mind that not all soils have all these layers. And some soils have astounding numbers of layers.  Soil horizons (Wilsonbiggs) CC BY-SA 4.0 Topsoil (O, A, and E horizons)
Topsoil refers to the uppermost 5-10” of soil. It has the highest concentration of organic matter and microorganisms. The majority of your plants’ roots can be found in topsoil. It is divided into three different layers. The organic surface layer, or O horizon, is where we find plant litter. In areas with waterlogged peat areas, we have the P horizon. Under that, we have the surface soil or A horizon. In some cases, leaching (or eluviation) can cause certain minerals to create a separate, lighter-colored layer between the topsoil and subsoil. This lighter layer is called the E horizon and it often contains a lot of silica. Subsoil (B horizon) While not as rich in organic matter as topsoil, the subsoil layer is where many minerals accumulate. This is especially true of aluminum, clay minerals, iron oxides, and some organic bits. The subsoil layer is commonly reddish-brown due to its iron content and it often has a distinctly different soil structure than the horizons above it. The subsoil layer is often overlooked, which is unfortunate since all garden plant roots make their way to this layer. When the topsoil and subsoil have gone through the same soil-forming conditions, the combined areas are called the solum. Substratum (C horizon) The substratum layer consists of partially weathered rocks that have not been affected by the conditions that created the layers above. It contains a lot of calcium carbonate and other soluble minerals and tends to be a lighter color than the layers above. This layer is often created by flooding and landslides. Bedrock (R horizon) Unlike horizon C’s rocks and boulders, which you can dig up, the bedrock layer is massive layers of rock that make up more of what we consider the earth’s crust. Other horizons Limnic soil (L horizon) occurs as a result of aquatic life. It contains the diatomaceous earth, sedimentary peat, and marl left behind when lakes and oceans dry up. You can also have a fluid or frozen water layer (W horizon) or man-made layers that block roots (M horizon). The next time you pass a construction site or look at an image of the Grand Canyon, take a closer look at all those layers and think about how they might affect plant roots. The closer you look, the more there is to see. How does fog affect your plants? Let’s find out.  Fog rolls into Seattle from the ocean (Patrick Rodriguez) CC BY-SA 3.0 First, what is fog? Fog is the low-flying equivalent of stratus clouds. It contains tiny droplets of water and ice crystals that have formed through condensation. This condensation occurs when the difference between air temperature and the dew point is less than 4.5°F (2.5°C). Dew point is the temperature that ambient air must reach to become saturated with water. When that point is reached, water particles start collecting around any dust, ice, pollen, or salt in the air. Unlike mist, which we can see through, fog tends to be harder to see through. Technically, fog reduces visibility to less than 0.62 miles, but who’s counting? There are several different types of fog, but I’ll leave that to you to explore. Let’s find out what all this moisture in the air does to our garden plants.  Foggy field (Shogun) Pixabay Time matters Fog diffuses sunlight, much the way smoke from fires does. [See Yellow Sky Days] Instead of simply shining downward, light particles get bounced around, allowing photosynthesis to occur in places where it normally might not. Of course, if there’s too much fog, photosynthesis is significantly reduced. Periods of fog often cause discoloration, stunting, and even wilting in crops such as wheat. These responses are temporary and they often disappear once the sky clears. Extended periods of moisture often increase the likelihood of disease. Bacterial head rot, black scurf, black spot, cucurbit scab, russeting, sooty blotch and flyspeck, and tomato gray wall are more likely in areas with frequent fog.
Foggy days are a good time to apply insecticidal soaps to manage cabbage aphids and other pests. And dormant oils are best applied just after a period of fog. Fog reduces topsoil drying, acts as a protective blanket during cold weather, and slows evapotranspiration, reducing the need for irrigation.
If you’ve never heard Eddie Izzard’s hysterical description of fog, check out his Dressed to Kill video. It cracks me up every time. With leaves falling from trees and swirling around our feet, today seemed like a good day to talk about leaf scars.  Horse chestnut stem showing seven bundle scars within a leaf scar (AnRo0002) Free Use When I say leaf scars, I am not referring to the ravages of battle or bad decisions. Instead, leaf scars occur naturally whenever a leaf falls from a tree. The information they ‘leave’ behind may surprise you. [Sorry, I couldn’t resist.] What are leaf scars? Leaf scars are the marks left behind on a twig after a leaf falls off. It is where the petiole, or leaf stem, was attached to the stem. As long as photosynthesis is taking place, the connection between leaf and stem is usually pretty strong. It has to be. Leaves flutter in the breeze, are battered by raindrops and send sugars produced through photosynthesis into the vascular bundle. But then things change. Scar formation At some point, a leaf becomes more of a burden than a sugar factory. In the world of plants, the process of getting rid of unwanted body parts is called abscission. Abscission can occur because of seasonal changes, or in response to conditions such as drought, shade tree decline, disease, or natural aging. That natural aging is called senescence. Whatever the cause, plants try to pull as many resources from leaves as possible before dropping them. This is why leaves change color in autumn. Once a leaf has been sucked dry, the petiole softens, and a protective barrier starts forming between the petiole and the twig. This area is called the abscission layer. After the leaf falls, the wound is covered by a protective corky material, leaving us with a leaf scar.  White ash leaf scar (Michael Ellis) CC BY 4.0 Other scars If you look closely at a leaf scar, you may see tiny holes arranged in a pattern. This area is called a bundle scar, and it is the torn vascular bundle. Buds often form just above leaf scars, and they leave scars of their own. They are called bud scars.  Leaf scars and buds on pecan stem (Paul Wray, Iowa State University, Bugwood.org) CC BY 3.0 Problems with leaf scars In some cases, diseases can take hold in leaf scars. Olive knot is one of several bacterial diseases that start this way. European apple canker is a fungal disease that can enter through leaf scars. Any time there is an opening, there is a risk of disease. That being said, you need to resist the urge to seal up plant wounds artificially. In most cases, this results in moisture being trapped against the wound. This slows the natural healing process and increases the risk of disease and rot.  Papaya leaf scar (Ameena104) CC BY 4.0 Botanists and plant aficionados use leaf scars to learn more about plants. Plants with small leaf scars tend to have small leaves. Plants with large, curved leaf scars tend to have bigger leaves. This is because a curved attachment can support more weight. Leaf scars can be brown, green, or red, depending on the species. They can be flat or rounded. In some cases, hairs can be seen around the leaf scar.
If you have a mystery tree, you may be able to use its leaf scars to help identify its family ties. Mid-November may feel like an odd time to be talking about caterpillars, but the delayed dormant period is a good time to start managing obliquebanded leafrollers before they have a chance to damage your fruit trees and it's good to be prepared.  Adult obliquebanded leafroller (Cheryl Moorehead) CC BY 3.0 Damage caused by obliquebanded leafrollers Obliquebanded leafrollers (Choristoneura rosaceana) cause different types of damage: their leafrolling behavior reduces photosynthesis; fruit feeding sets the stage for brown rot and deformed fruit, and early stem-feeding can significantly reduce crop size. These pests are primarily attracted to members of the rose family, specifically cherry, pistachio, and plum trees. They have also feed on apple, chestnut, hazelnut, pear, and stone pine trees, as well as blueberries, cane fruits, strawberry plants, and sunflowers. Several popular ornamentals also host these pests. Obliquebanded leafroller description Obliquebanded leafroller adults are light- to reddish-brown moths with a unique squarish back end and something of a ridge just behind the head (thorax). They are a mottled tan to brown with wide, offset (oblique) bands of alternating color. The wingspan ranges from 3.0 to 5.5 inches across, with the females being significantly bigger than the males. If you were to get your hands on one of these moths, you would be able to see that the forewings tend to be much darker than the underwings. Obliquebanded leafroller moths look like fruittree leafrollers (Archips argyrospila) and three-lined leafrollers (Pandemis limitata). Caterpillars are green to yellowish-green with dark heads. [Sorry, I couldn’t find a photo I could use.] They average one inch in length. These garden pests have the unique behavior of crawling backward when disturbed and dropping to the ground with the aid of a silk thread. Left to their own devices, obliquebanded leafrollers, being true to their name, will fold or roll leaves together to create a protective tent while they feed. Obliquebanded leafroller lifecycle Masses of 200-900 eggs are laid on the tops of leaves and then covered with a protective wax. They hatch in a week or so. The first instar larvae crawl to safer places, such as the underside of leaves, in buds, or under the calyx of fruit. [The calyx is the protective growth that encases flower buds.] They may also balloon themselves to nearby plants using a silk thread. As these caterpillars go through six instars, they roll leaves around themselves for protection as they feed. Obliquebanded leafrollers overwinter as second-instar caterpillars in crevices of trees, under flower bud scales, and bark. Eventually, they drop to the ground, where they pupate in the soil.  Obliquebanded leafroller pupa (Beatriz Moisset) CC BY-SA 4.0 Obliquebanded leafroller management
Most management practices take place in spring and summer. As young caterpillars begin to emerge in spring, you can spray Bacillus thuringiensis on them, followed by spinosad sprays in summer. You can also use pheromone traps to monitor for adult moths. Assassin bugs, Exochus ichneumon wasps, lacewings, minute pirate bugs, and parasitic Goniozus wasps will attack obliquebanded leafrollers. You can attract these garden helpers by adding insectary plants to your landscape and avoiding the use of broad-spectrum pesticides. During the delayed dormant period, be sure to spray your trees with the appropriate dormant oil to help control these and other pests. The delayed dormant period is after full dormancy but before the green bud stage. You can also reduce the problems associated with obliquebanded leafrollers by removing water sprouts and thinning fruit properly. If you’re an early riser like myself, you know that the pre-dawn morning air is softer and sweeter than any other time of day. There are fewer car sounds, and you can hear birds, bees, and rustling leaves. Somehow, standing outside in a quiet morning hour, I feel as though anything is possible. As the day progresses, it becomes more difficult to hear those natural sounds, partly because humanity is noisy and partly because I get busy and forget to listen for them.  Sunrise in the garden (Kate Russell) Research has shown that natural sounds can reduce pain and improve mood. They even make us kinder and less likely to feel annoyed. So how can you create a soundscape? And how can we add natural sounds to homes? Let’s find out. It’s no surprise that we plant gardens for fruits, herbs, or vegetables, colorful flowers, or fragrant aromas. We’ve already talked about sensory gardens and scent gardens, but you can create a garden for its sounds, too. Barriers against noise Add fencing, hedges, or a tree line to block the sounds of traffic and other distractions. There are other benefits to these noise barriers. Some hedges are fragrant, while others produce food. Ornamental Thuja plicata ‘Atrovirens’ smells like pineapple when crushed. Or you can harvest blueberries from a berry hedge. Just be careful with bamboo. While some varieties can grow very tall rather quickly, they can spread and become invasive. Keep in mind that sound can travel around barriers.  Fencing blocks noisy neighborhood sounds (Kate Russell)
 A birdbath will attract a variety of garden visitors (Kate Russell) While adding bird feeders is often touted as a good way to attract our avian friends, research is beginning to show that these unnatural food sources are disrupting natural migration patterns and increasing the incidence of bird diseases. Rather than being part of that problem, reach out to your local native plant society. They can help you identify the best plants for attracting native birds and beneficial insects without creating problems. Those native plants often have the added advantage of requiring less effort on your part.
 Oat and wheat heads rustle in the breeze (Kate Russell) Annual honesty (Lunaria annua) provides lovely flowers in summer and bright fluttering sounds through autumn and winter. Love-in-a-mist (Nigella damascena) provides beautiful flowers and fairy rattles that remain standing for quite some time.
Indoor soundscapes Indoor soundscapes are trickier to create. Unless you open the window, there aren’t any breezes. And you probably don’t want any birds or buzzing insects flitting about in your kitchen. In fact, I was unable to find any advice online aside from adding yet another app to my daily life. No thanks. As a child, I had a sequence of pet parakeets. I loved them and I like to think that I took good care of them. As an adult, however, I would never put a bird in a cage. Heck, even my chickens had tons of running around room. But now that I live in an apartment high-rise, things have changed. I could do what my upstairs neighbor does and feed the birds to get more bird sounds. Of course, that also means more bird poop on my balcony and it messes with the birds’ natural cycles. That being said, I do have a hummingbird feeder, which brings the sound of their wings to my daily life. I could add a native seed-producing plant to my balcony. I’ll have to check with my local native plant society for that one. Cats and dogs certainly add natural sounds (and love) to your home. A fish tank will add the sound of moving water to your home, but I don't know if fish can love people or not.  Kitten playing with aquarium fish (Irina Kukuts) Pixabay Probably the easiest way to add natural sounds to your home is with an indoor tabletop fountain or waterfall. There’s just something about the sound of trickling water that soothes us humans [and drives beavers into a dam-building frenzy]. Most of these tabletop water features are quite small and easy to care for, making them perfect for apartments. You may even be able to grow some watercress in one. I'm not sure if it would work, but it might be fun to try.
Add some natural sounds to your environment for a more relaxed, happy, and healthy day. Did you know that plants can hear? We’ll talk about that tomorrow. Nutrient deficiencies (and toxicities) interfere with plant health. And it’s not a simple matter of being present. Soil can be chock full of nutrients. And plants may still be deficient.
Negatively charged clay and organic matter can attract and hold positively charged nutrients, such as calcium and potassium. Clay, in particular, holds onto more water and nutrients than other soil textures. Sometimes, it holds on so tightly that plants cannot access the food they need. Positively charged sand and water hold on to negatively charged particles, such as phosphorus and sulfur. The ability of a plant to pull nutrients in also depends on soil texture, structure, and pH. Nutrient deficiencies and soil composition We describe soil by its texture (size) and structure (arrangement). Soil texture can be large (sand), medium (loam), or incredibly small (clay). Soil texture determines how well it drains. It also impacts which nutrients are easy for plants to absorb. Soil structure describes how minerals clump together with microbes, earthworms, and organic matter. Spaces, called macropores and micropores, occur within and between these particles. Compacted soil makes it difficult for plant roots to get to their food. Sandy soil often allows water and nutrients to drain away before plants can get to them. Soil pH ranges from 0 to 14, with lower numbers indicating acidity and higher numbers indicating alkalinity. More nutrients are available, and there is more microbial activity when soil pH is between 6.0 and 7.0. Most plants can survive in soil pH from 5.2 to 7.8, but each species has a narrower range that allows them to thrive. As plants absorb these anions and cations, the soil pH changes slightly. Too much or too little of certain minerals in the soil may interfere with nutrient availability. Mulder’s Chart illustrates this concept nicely. Nutrient imbalances Without the necessary nutrients, plants cannot thrive. But too much of a good thing can be a bad thing too. If there is a lot of a specific nutrient in your soil, plants may take what they need, or they may eat themselves to death. It depends on the nutrient and the plant species. In my old yard, the soil was compacted clay with a severe iron deficiency. Since plants use iron to help them absorb several other nutrients, it didn’t matter that the previous owner kept adding a balanced fertilizer. As soon as the plants used any iron present, there was still too much of everything else. So, how do you know if there’s a deficiency, and what can you do about it? Lab-based soil tests are the only way to know if your soil is deficient. Over-the-counter tests look great, but they cannot provide accurate information. Luckily, laboratory soil tests are not expensive. They cost about the same as a large bag of fertilizer and can save you more than that by preventing overfeeding and poor plant health. All too often, people see what they think is a nutrient deficiency, so they apply a 10-10-10 fertilizer. At first, everything looks better. But it never lasts. That is because the balance of nutrients in the soil is what matters. Symptoms of deficiency Nutrient deficiencies are often present in specific parts of a plant. Some nutrients are more mobile than others. Plants can move mobile nutrients, such as nitrogen, to wherever they need them. Older leaves start looking chlorotic when plants move nutrients to support new growth. The opposite is true for immobile nutrients, such as calcium. These nutrients require significant amounts of water to move around within a plant, so symptoms first occur in fruit and new growth. Let’s take a closer look. Magnesium, nitrogen, phosphorus, and potassium deficiencies are visible on older leaves or near the bottom of the plant. We see molybdenum and sulfur deficiencies in the whole plant or around the middle. New growth and the tops of plants exhibit boron, calcium, copper, iron, manganese, and zinc deficiencies. Deficiency symptoms can overlap, making the diagnosis a bit tricky. This table may help.  What can you do to prevent or correct deficiencies?
First, get your soil tested. You can’t know what’s going on without it. Once you have your test results in hand, only add what’s needed. If toxicities are present, you can reduce those numbers over time by harvesting as much as possible. Plant and harvest heavy feeders, such as cereals, melons, or squash, to help reduce excess nutrients. In some cases, such as potassium deficiencies, the damage to an individual leaf is irreversible. But you can still improve conditions in general, helping the plant recover. The following good practices will help keep your plants healthy and well-fed:
Apical dominance is why trees and many other plants end up tallest in the middle, but there’s more to it than that.
Imagine, if you will, that every bud on a young tree grew into a full-sized branch, and that each twig from each branch also grew into a full-sized limb. You can see how convoluted things would get rather quickly. Apical dominance is what keeps that mess from happening. Apical dominance refers to the way that central stems are dominant over other stems. It also describes why branches are dominant over their twigs. It makes sense. If the twigs were bigger than the branch, it would eventually break. If side branches were bigger than the central trunk, trees and shrubs might not get enough sunlight. Let’s see what makes plants behave this way and learn how we might use this behavior to our advantage in the garden. Apical dominance and sun exposure Plants need sunlight to grow. The tallest plants get the most sunlight. By growing upward first and then outward, a plant’s chance of survival is increased. For conifers, which often grow at higher latitudes where sunlight is lower on the horizon, the triangular Christmas tree shape provides the greatest amount of sunlight. For deciduous trees, growing at lower latitudes with more overhead sunlight, the rounded canopy provides the most sun exposure. In both cases, the woody structure supports the leaf canopy that allows for photosynthesis. Photosynthesis is all about sugar production. And, contrary to popular belief, sugar is the reason behind apical dominance. Apical dominance and terminal buds The buds at the ends of stems are called terminal or apical buds. This does not mean they are waiting on a visit from hospice. Just the opposite. This is where meristem tissue is found. Meristem tissue is new, undifferentiated life. This is where growth happens. Even though growth is happening at all the buds and twigs along a stem or trunk, the ones at the top and/or ends have priority. We used to think that this happened because of a plant hormone, called auxin, but research has shown that it is the growing tips’ demands for sugar that robs their neighbors of enough sugar to grow equally fast. If apical buds are removed, lateral buds are free to demand more sugar and grow more quickly. This is where pruning, coppicing, espalier, pollarding, and tree training come in. Apical dominance and pruning If you pinch off the central stem of a basil plant, just above a pair of leaves, it will grow to be bushier and produce more delicious leaves.
If you apply production pruning to your nectarine tree, it will produce significantly more fruit. Different fruit and nut trees benefit from different types of tree training, but the results are the same: healthier, more productive trees. Espalier uses the same concept but in two dimensions, rather than three. Apical buds are pinched back to stimulate side growth.  Pollarded trees in Spain (Kate Russell) Pollarding and coppicing apply the same principle but on different parts of a tree. Coppicing refers to the practice of cutting small trees and shrubs back to ground level regularly to harvest several thin stems that are useful for basket-making, firewood, and wattle-and-daub fencing. Pollarding is the same practice but done higher up in a tree to promote new overhead growth.
How are you putting apical dominance to work in your garden?
Midge/gnat life cycle You may have seen swarms of tiny insects over a birdbath or wet soil some summer evenings. These swarms are mating dances that may last for several days. Some of these swarms can get big enough to hear, and they may look like clouds of smoke from a distance. In some cases, roads can become so slick with gnats that accidents occur. These insects may also sun themselves on the side of a house in such numbers that it appears coated.
Biting midges Biting midges (D. Ceratopogonidae) are blood-suckers. Like mosquitoes, these midges need blood to reproduce. This group includes black flies, no-see-ums, and sand flies, which inflict painful bites and can transmit human diseases. Some members of this group also suck the bodily fluids from insects. Many of them also drink nectar. Larval biting midges are sometimes called bloodworms because they contain blood.  A midge sucks the bodily fluids from the knee of a mantis as it eats a bee (JonRichfield) CC BY-SA 3.0 Phantom midges Phantom midges (D. Chaoboridae) are also known as glassworms. You can see why  Phantom midge larva (Piet Spaans) CC BY-SA 2.5 Most phantom midge adults do not eat. Those that do only drink nectar. Phantom midge larvae are rather bizarre in that their antenna have evolved into grasping organs that crush prey and other foods, somewhat similar to the hands of a mantis.  Male phantom midge (Richard Bartz) CC BY-SA 2.5 Nonbiting midges
Several midges create galls and damage buds, leaves, or roots. Some of the more common midges, and the plants they damage, include:
When midges damage plants, the first signs will be small discolored areas, general failure to thrive, and wilting. Over time, the effects of midge feeding and burrowing can significantly reduce crop size. It also makes plants susceptible to other pests and diseases. Midge management Removing standing water is always a good idea, and not just because of midges. Mosquitoes can be more than just a summer annoyance. These tips can help manage both midges and mosquitoes:
Interesting fact: chalcid wasps (the ones who give us figs) are midge and gnat predators. If midges have become patio pests, turn off your lights or get one of those bulbs that claim to not attract insects. [I’m not sure how well they work. Have you had any experience with them? I’d love to hear about it in the comments.] Beneficial midges Some midges are major pollinators of the cocoa tree, so they aren’t all bad. There are also predatory midges. Aphid midges (Aphidoletes aphidimyza) devour aphids, while predaceous gall midges (Feltiella acarisuga) protect your plants against a surprising number of spider mites. May all your midges be beneficial, and gnats be absent from your landscape. Most of us are unfamiliar with pawpaws. Even my computer didn’t recognize the word. This is a shame because pawpaws (Asimina triloba) are North America’s biggest edible tree fruits. We don’t see them in stores because they bruise easily and start fermenting as soon as they ripen.  Pawpaw fruit and leaves (Scott Bauer, USDA) Public Domain Tagged with a variety of common names such as Indian custard, Hoosier banana, custard apple, and Quaker delight, the word pawpaw is believed to be from the Spanish word for papaya. They are said to taste like a combination of banana, citrus, mango, and pineapple, with a consistency similar to Hachiya persimmon. These North American natives are commonly found from the Great Lakes region south to the Florida panhandle. More often than not, pawpaw trees are completely overlooked, their bounty left for bears, gray foxes, and other wildlife. I think that it’s time we all knew a little more about these cousins of cherimoya. Pawpaw tree description Pawpaws are large shrubs or deciduous trees that can reach 35 feet in height but are commonly much smaller. They tend to form thin-trunked colonies in shady bottomlands, but will not thrive in full shade. They spread using root suckers. Seed reproduction only rarely results in viable trees in the wild. They have large, simple leaves that grow in clusters at the ends of branches. When bruised, the leaves are said to smell similar to green bell peppers. Pawpaw flowers are reddish-purple and can be 2” across. Because these flowers smell more like carrion than fruit, blowflies and carrion beetles do most of the pollinating  Pawpaw flower (DickClarkMises) Public Domain The fruits, which are berries, are large yellowish-green to brown ovals, similar to mango or papaya. They have pale to bright yellow flesh and can be up to 6” long and weigh more than one pound. Each fruit contains several large seeds. Ripe fruits fall from the tree, but you can pick them just before that happens.  Pawpaw fruit (Manuel.conde) Public Domain
Pawpaws can be grown in USDA Hardiness Zones 5—9. While it is easiest to start your tree from root suckers or bare rootstock, you can use seeds that have been kept moist and stratified in cold storage for 2 or 3 months. The problem with seeds is that each seed is genetically different from its parent and siblings, so there’s no way to know for sure what you’ll be getting. On the flip side, root suckers have very few roots, while seedlings started from seeds have substantial taproots that help them get established.
Pawpaws can be grown in containers at first, but will eventually need to be put in the ground to stay healthy and productive. Since fruit is produced on new growth, annual pruning is important. Being deciduous, it is easy to prune pawpaw trees in winter. Pawpaws should be fed in early spring and again in early summer. Pawpaws prefer slightly acidic, moist soil with good drainage. These trees grow best in sites with strong morning sun and afternoon protection. Problems with pawpaws Pawpaws suffer from surprisingly few diseases or pest problems when compared to other orchard fruits. The most common problem faced by pawpaw growers is insufficient pollination. While pawpaw trees have both male and female flowers, they cannot pollinate themselves, so you will need more than one tree. You can improve pollination rates by hand-pollinating. Commercial growers have been known to spray their trees with fish emulsion or hang chicken necks in their trees to attract the appropriate pollinators. I don’t see myself hanging chicken necks in trees. Ever. But a cluster of low-maintenance pawpaw trees along a back fence sure sounds appealing. Frogeye leaf spot refers to three different fungal diseases. One attacks soybeans, one infects peppers, and the other prefers your apples. Let’s look at all three, shall we?  Frogeye leaf spot on tobacco (Clemson University - USDA CESS, Bugwood.org) CC BY 3.0 Frogeye leaf spot in apples Frogeye leaf spot in apples is caused by Botryosphaeria obtusa. This pathogen is also responsible for cankers in apples, cranberries, and quince, and dead arm disease in grapevines. Apple leaves infected with frogeye leaf spot develop purple specks that expand into brown spots with purple margins, hence the name. Left to progress, frogeye leaf spot causes black rot in your apples.  Black rot in apple (University of Georgia Plant Pathology, University of Georgia, Bugwood.org) CC BY 3.0 The only treatment for frogeye leaf spot in apples is to prune out infected branches, sanitizing your pruners between each cut. Infected plant material should be thrown in the trash and not composted. To prevent this disease from continuing, all fruit should be removed from the tree. As a gardener who loves her fresh apples, this can be a sad fact. Hopefully, those apples are ripe enough to eat and use for applesauce. The fungus won’t hurt you, and you can cut out the bad bits, but this disease can cause significant leaf and crop loss. Frogeye leaf spot in peppers Frogeye leaf spot in peppers is caused by Cercospora capsici fungi. Also known as Cercospora leaf spot, this disease infects eggplant and tomatoes, along with peppers. It starts as tiny, grayish-brown spots with dark margins on leaves, petioles, and stems. These spots eventually grow to one-half inch in diameter. If you look at one of those lesions with a hand lens or microscope, you will see tiny black flecks. Those flecks are fungal spores.  Frogeye leaf spot symptoms on pepper leaf (David B. Langston, UGA, Bugwood.org) CC BY 3.0 us Frogeye leaf spot in soybeans Frogeye leaf spot in soybeans is caused by Cercospora sojina. This disease is found in many parts of the world and has been expanding its range northward from the southern US. Frogeye leaf spot in soybeans causes small, somewhat rounded, or angular reddish-brown to purple lesions on upper leaf surfaces. The interior of these lesions is often gray or tan. As the disease progresses, leaves become tattered and fall off. Pods and stems can also become infected and covered with dark-rimmed lesions with reddish-brown centers. The lesions also produce ethylene gas which increases leaf loss. And nobody wants rotting soybeans.  Frogeye leaf spot lesions on soybean leaf (Maggilautaro) Public Domain This disease can occur at any time during a soybean plant’s lifetime and several different stages of the disease may occur at the same time on different plants. The pathogen overwinters as mycelium in the soil, seeds, and plant residue, and remains viable for up to two years.
In each case, frogeye leaf spot is most likely to occur in situations with warm, humid conditions or long rainy seasons. To reduce the chance of frogeye leaf spot occurring in your garden, use these tips:
Fungicides can also be used, but the frogeye leaf spot pathogens have already developed resistance to some of those treatments (strobilurins). As temperatures continue to rise, frogeye leaf spot is expected to become a more common problem. Three-lined potato beetles are more likely to damage your tomatillos and cape gooseberries than your potatoes, which is why they are also known as tomatillo leaf beetles. But they will cause problems for your tomatoes and potatoes, too. Both adults and larval forms are voracious leaf eaters.  Three-lined potato beetle (Whitney Cranshaw, CSU, Bugwood.org) CC BY 3.0 Originally from North and Central America, three-lined potato beetles (Lema daturaphila) are now found in many parts of North America, Australia, and South Africa. Although these pests are relatively rare, so far anyway, they can cause significant damage. Three-lined potato beetle identification As their name states, these invasive pests have three black stripes that run lengthwise on their mustard-colored to bright yellow wing covers. They are ¼” long and have an orange head and prothorax with two black spots. The prothorax is the bit just behind the head. Larvae look like dark gray slugs with black heads and three pairs of prolegs. Three-lined potato beetle larvae have a nasty habit of covering themselves with their excrement to deter predators. I imagine it works. Eggs are oval and orange and laid in clusters on leaves.  Three-lined potato beetle egg mass on tomatillo leaf (Whitney Cranshaw, CSU, Bugwood.org) CC BY 3.0 Three-lined potato beetles look similar to western corn rootworms (Diabrotica virgifera) and striped cucumber beetles (Acalymma trivittatum), both of which are more likely to be found among your cucurbits and corn. Also, cornworms are smaller than three-lined potato beetles, while cucumber beetles are larger than both. Colorado potato beetles (Leptinotarsa decemlineata) may be found around potatoes and other nightshade plants, but their shape and color are different
Damage caused by three-lined potato beetles Adults tend to travel and feed by themselves, so the damage they usually cause is minimal. As they eat, they may create holes in leaves, or they may remove entire leaves. The larvae, on the other hand, feed in groups and can cause considerable damage. Like other creatures who have evolved to eat members of the nightshade family, they are immune to the lethal tropane alkaloids found in the leaves of these plants.  Three-lined potato beetle larvae feeding on tomatillo leaf (Whitney Cranshaw, CSU, Bugwood.org) CC BY 3.0 All this leaf-feeding means less photosynthesis, weakened plants, and reduced crop size. It also makes plants more susceptible to other pests and several diseases.
Three-lined potato beetle lifecycle These garden pests overwinter as adults or as pupae in the soil, depending on the local climate. Adults become active in late spring through the summer, laying eggs on host plants. The larvae usually hatch in early summer, though there can be two generations each year. Three-lined potato beetle management Hand-picking the caterpillars is your best defense since adults can fly. Simply pluck them from your plants and drop them in a container of soapy water or feed them to your chickens. Row covers can protect plants from three-lined potato beetles, and eliminating weeds in the nightshade family will make your garden less appealing to these pests. |
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