Garden Word of the Day
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Butt rot? Really?
Yes, Virginia, there is a fungal disease of almond trees called butt rot. Its full name is Ganoderma root and butt rot, and it can kill your tree.
When most people say “butt” they mean a certain mammalian body part. When botanists and gardeners say “butt” they mean the base of a tree. In either case, butt rot is not something you want.
Butt rot is common in Europe and California but can occur anywhere. This disease is responsible for the complete removal of many orchards. Butt rot kills young trees outright. Removing infected trees is expensive and necessary to prevent the disease from spreading.
Three different bracket or shelf fungi from the Ganoderma genus: G. adspersum, G. brownii, and G. polychromum are responsible for butt rot. Ganoderma root and butt rot (G. applanatum) affect oak trees. All of these fungi devour wood.
Butt rot symptoms
At first, infected trees fail to thrive. Then they decline. Shelf-like conks may grow along the trunk or clefting at graft union. Clefting describes the way the two halves of a graft union peel apart. You may see branch dieback within the canopy, and leaves may be smaller. The rooting of infected trees tends to be shallower than healthy trees. Eventually, the tree will break off at ground level, so keep your distance.
This disease infects the canopy and trunk, causing both heartwood and sapwood to rot. This makes trees structurally unstable and unsafe to be around. Eventually, branches start breaking off and the tree dies. Before that happens, there are steps you can take to prevent butt rot.
Butt rot management
The fungal spores responsible for butt rot are spread on the wind and enter through wounds in the bark. Keeping the bark intact is the best way to prevent butt rot. Keep edgers and mowers at a distance, and remove rubbing branches and unnecessary tree supports.
As soon as there is a wound, fungal spores can enter. Before you paint over that wound, you need to know that that can cause even more problems by holding moisture against the trunk. If an injury does occur, let the tree heal itself. A callus will form. Hopefully, before pests or pathogens use it as an entrance.
Good drainage is critical. You can improve drainage by mulching and top-dressing around trees with aged compost. Leave at least 8-12” bare ground between tree trunks and any amendments.
Other preventative measures include:
If you have a tree with conks, contact a certified arborist. They can inspect the tree for structural integrity and determine the cause and extent of any infection.
Fusicoccin, or constriction canker, is a fungal disease of almonds and peaches.
You may find this word easier to say than to read at first. It is pronounced FUSE-ih-koksin. Once you say it aloud a few times, it gets easier.
Fusicoccin is a disease that forces plants to open their stomas. Stomas are tiny breathing holes found most often on the underside of leaves, but stems and other tissues can also have stomas. Plants use stomas to create bubbles of high humidity which evaporate, pulling moisture up a plant’s vascular system from the ground. It’s pretty amazing when it works the way it should. When stomas stay open, plants start drying out.
Fusicoccum amygdali fungi are responsible for this disease. These fungi produce chemicals that acidify plant cell walls, causing the stoma to open permanently. They enter plants through blossoms, bud scars, fruit scars, leaf scars, and stipules. Any fresh opening is vulnerable.
The first sign of fusicoccin is wilted leaves and shoots, followed by long, brown cankers on infected buds and nodes. These symptoms usually appear in early summer. They become worse as the disease progresses. You may see constricted areas at the base of infected shoots. Gum may be seen oozing from infected areas, but don’t use that as a diagnostic tool since gumming is a frequent response to several diseases and disorders. Fruit on infected stems tends to shrivel up and fall off the tree, further spreading the disease.
Research has shown that certain fungicides can control this disease. But many of these products can cause birth defects, cancer, and infertility.
Another option is to fight fire with fire. Or, in this case, fight fungi with fungi. Trichoderma harzianum and Trichoderma viride are antagonistic fungi that work as biofungicides, parasitizing fusicoccin pathogens. Of course, they will also damage your homegrown mushrooms. As gardeners, we must choose our battles. You can buy these biofungicides online or from your local garden center.
To prevent fusicoccin, keep trees healthy by applying biofungicides according to package directions and buying resistant varieties whenever possible. If fusicoccin appears on your peach or almond trees, remove infected branches by cutting several inches below the affected area and throwing those twigs in the garbage. Be sure to sanitize the pruners between each cut to prevent infecting healthy tissue.
Hull rot isn’t a warning to sailors, but your almond tree may be at risk.
If you grow almonds, your tree goes through several stages before producing a crop. As deciduous trees, winters are spent bare and quiet. In late winter or early spring, a riot of colorful blossoms unfolds, followed by leafing out.
Those flowers will fall, and fuzzy green almonds will start to grow. As they ripen, they get fat. Ultimately, the hulls dry and split open. When that occurs, hull rot may invade the nuts, threatening the life of your tree.
Hull rot is a fungal disease initiated by Monilinia, Rhizopus, and Aspergillus niger. Aspergillus niger also causes sooty mold. If you notice leaves on shoots withering and dying, look more closely.
Hull rot symptoms
You may see brown areas on or in the hull (Monilinia). You may see black fungal growth inside the hull, between the hull and the shell, or on either side of the edge that opens (Rhizopus stolonifer). Or, you may see black spores between the hull and shell (Aspergillus niger). Each of these is a type of hull rot.
These fungi produce toxins that kill fruiting spurs and the twigs to which they are attached. Almonds on infected branches are more difficult to remove than healthy nuts. Ultimately, shoots, strikes (fruiting wood), and lower limbs die back.
Hull rot prevention and management
Healthy trees are less likely to become infected in the first place, so care for almond trees properly with these tips:
Trees infected with hull rot need help from a professional arborist. The fungicides effective against hull rot are generally unavailable to the public.
Hopefully, your almond tree will never become infected with hull rot.
Golden pearls look like tiny tomatoes or yellow currants, but they taste more like cherries and can make you very sick if you eat them before they ripen.
Native to Africa and Europe, golden pearls (Solanum villosum) are now found in Australia and North America. Also known as golden wonderberry, hairy nightshade, red nightshade, and woolly nightshade, this sprawling annual is considered a weed by many.
These members of the nightshade family produce clusters of yellow or orange berries that are sweet and edible when ripe and can make you very sick if eaten when unripe. The hairy leaves are also edible, but similar to poke sallet, the leaves must be boiled a couple of times to be safe to eat.
Golden pearls plants
Golden pearls make nice container plants and they begin producing fruit early in the growing season and will continue into autumn. Golden pearls that are grown in containers will produce smaller fruit than plants growing in the ground or raised beds. These plants tend to be bushy and can grow 36” tall.
How to grow golden pearls
Seeds are best started indoors or in a protected spot once temperatures begin to rise and your last frost date is behind you. Only cover seeds lightly, if at all, with soil. Keep them moist using a mister or water from the bottom with a tray until they sprout. This will keep them from being flooded into a corner.
Seeds are slow to germinate, taking 20 to 40 days, but they grow quickly once they get going. Plants should be spaced 24” apart and watered regularly. They prefer moist soils and can tolerate partial shade though they grow best in full sun.
Golden pearls are not as sweet as groundcherries, but they just might make a nice addition to your garden, landscape, or patio.
What can leap small buildings and decimate your garden before you’ve had your first cup of coffee?
Yes, Bambi’s family can destroy a garden in short order, and keeping them out can be challenging. Waking up to find your prized hostas, delicious strawberries, and crisp lettuce plants eaten down to nubs can be very frustrating. The more you know about deer, the better you can protect your herbs, trees, and produce from these athletic grazers.
Yes, they are beautiful. And who hasn't wanted to pet a spotted fawn? Before you start defending a deer’s right to eat and live, you need to know that deer often carry Lyme disease, as well as ticks and fleas. Other diseases deer may carry include chlamydiosis, leptospirosis, Q fever, salmonellosis, and tuberculosis, just to name a few. The real problem with deer is their appetites. They can ruin a hedgerow, eliminate entire garden beds, and kill trees in their search for food.
To keep deer out of your garden or landscape, you have a few options.
Some municipalities offer culling services. In this case, hunters come to your property and shoot some of the deer. This reduces the number of deer feeding on your tomato plants and makes the remaining deer a little more cautious, for a while, at least. Many times, the venison is then given to local charities to help feed those in need.
Many people see this as cruel but consider my story. Culling and hunting were banned many years ago while I lived in Virginia. At that time, I was volunteering with Fish & Wildlife, doing hawk-banding and eagle counts, so I was spending a lot of time out in the woods, hiding in a blind. What I saw was heartbreaking. The deer were starving to death. There were simply too many of them. They were mangy and diseased and suffering. People had already killed off many of the predators that would have restored the natural balance and deer, being prey animals, are very prolific. They had bred themselves into starvation. It made the bullet from a hunter’s gun look humane by comparison.
When my mother lived on 97 acres in Upstate New York, my then brother-in-law would hunt a few deer and we would get a Christmas box of frozen, wrapped venison. It was delicious, but my mother never won the war against deer in her rural garden. Her plot was too far from the house and she wasn’t willing to install adequate fencing.
A healthy adult deer can leap over anything lower than 10’ tall. Most people don’t want a 10’ fence around their garden. Some people have found that a solid 6’ fence topped with an additional three- to four-foot mesh works, presumably, because the deer can’t see what they’d be jumping into. Electric fences can be somewhat shorter, though they do require regular monitoring. I can tell you from personal experience, touching a hot wire isn’t something you’ll forget any time soon. The advantages of electric fencing are they are less obtrusive, cost less than solid fencing, and they don’t actually harm the deer. [I recently heard about electronic posts that smell like acorns and deliver a shock when touched. Does human ingenuity ever end? I hope not!]
Another tricky fencing solution is to use two 4- to 5-foot fences placed four feet apart. This is believed to confuse the deer since it is difficult for them to clear both fences and they don’t like to feel boxed in.
If garden-wide fencing isn’t an option for you, tall cylinders of wire fencing can be used around individual beds or plants to protect them from deer feeding. You may also want to try stringing a fishing line strategically around your garden and landscape where deer frequently walk. They will run into the invisible barrier and feel threatened. Just watch out you don’t clothesline yourself!
If you grow apples or cherries, beans or beets, blueberries, broccoli, cabbage, cauliflower, pumpkins, spinach, well, if you have a garden and there are deer in the neighborhood, there’s going to be a problem. Deer will always go for arborvitae, azaleas, hardy geraniums, hosta, rhododendrons, roses, and tulips. There are some plants, however, that deer don’t eat.
By installing plants that deer are unlikely to eat throughout the landscape, deer should be less likely to cause significant damage. These plants include most herbs, mint and lemon balm, members of the onion family, artichokes, asparagus, eggplant, fennel, figs, lavender, and rhubarb. They also seem to avoid plants with fuzzy leaves, such as lambs ear or yarrow, prickly plants, and plants toxic to deer. That list includes bleeding hearts, daffodils, false indigo, hellebores, monkshood, poppies, and spurges.
There are also plants that deer would rather not eat, but will if they are particularly hungry. This group includes tomatoes, peppers, and potatoes, squash, cucumber, Brussels sprouts, cilantro, horseradish, okra, melons, and chard. Keep in mind that tender, young shoots of nearly every plant are considered fair game by deer, and deer do not read reports or studies, or blog posts about what they do and do not eat. If your local deer love artichokes and horseradish, you’ll have to figure out ways to protect them. [Rutgers University offers an extensive list of what deer do and do not generally eat.]
Deer spook easily, so sudden noises and movements can make them turn and run. You can use plastic bags tied to the tops of poles, old CDs hanging in trees, pinwheels, or windchimes. Like scarecrows, scare tactics lose their effectiveness over time. Commercial growers use air cannons but your neighbors probably wouldn’t appreciate that one.
Garden hoses attached to motion-detectors are said to be effective. I can’t help but picture a herd of deer lounging on my lawn, nibbling garden treats and enjoying the cool spray, like a bunch of kids playing in the sprinklers on summer vacation. I could be wrong. I had a neighbor, many years ago, who entertained the neighborhood children each Halloween with well-thought-out theatrics, which often included a leaf-blower attached to a motion detector. It just might work to protect your garden plants, too.
The big stink
Deer rely heavily on their sense of smell and they avoid areas frequented by predators. If they smell predators, they will generally go down a different path. You can find countless recipes online for DIY deer repellants. I have no idea how well any of them work, and some of them sound awful. Personally, I have used Bobbex-R with good results. It stinks (to humans) for about 45 minutes, then goes away. Deer, rats, and squirrels tend to avoid it for several weeks. I imagine that other commercially available deer repellants work in much the same way.
Pungent herbs and scented geraniums are known to repel deer, as does cheap perfume sprayed on strips of fabric and zoo poo from the lion’s den. If you have dogs, they can help discourage deer from grazing in your garden. Other tips to reduce deer damage include:
And be sure to switch things up. Deer can get used to just about anything, especially if they are hungry. If you move things around and cycle through different deer repelling tactics, they are more likely to be effective.
Tell us your deer story! How do you keep deer out of your garden?
Daddy Longlegs and Cellar Spiders
We’ve all seen them – spiders with tiny, little bodies and long, delicate legs. What you may not know is that daddy longlegs aren’t actually spiders. And what many of us call daddy longlegs are actually cellar spiders. Or crane flies.
Before we get into the differences and similarities, we need to put aside a common misconception. Urban myth states that daddy longlegs have the most potent venom of any spider and that the only reason they aren’t a danger to us is because their fangs are too small to bite us. False on both counts. Daddy longlegs can bite you and their bites won’t hurt you. Their venom is relatively weak.
To figure out which insect you have, you should first ask yourself if it has wings.
If you see a daddy longlegs with wings, it’s a crane fly. Crane flies are the recipient of a different urban myth. As children, we called them mosquito-eaters because we thought they ate mosquitoes. We were wrong. Crane fly larvae feed on the crowns, leaves, and roots of your lawn and other members of the grass family (Poaceae or Gramineae). This includes barley, corn, lemongrass, millet, oats, rye, sorghum, and wheat. Crane flies are pests. If there are no wings present, it’s a spider.
The long-legged spiders most of us see are cellar spiders. These spiders have oval- or peanut-shaped bodies and extremely long, delicate legs. If you are willing to get close enough to see [and I urge you to, these creatures are amazing up close!] they may have 6 or 8 eyes, arranged in groups of 3 or 4, respectively. Cellar spiders may be gray, tan, or brown and they often have chevron markings. These spiders hang upside down from their webs and will shake them when they feel threatened.
Cellar spiders build messy, irregularly-shaped webs, which are often found in caves, under loose bark, and in the upper corners of many living rooms, garages, and attics. These webs are not sticky, just confusing. Prey become entangled, are bitten, and then thoroughly wrapped up to be eaten later. After being consumed, prey are removed from the web and their empty husks are dropped to the ground.
Rather than feeding exclusively on flies and gnats, cellar spiders prefer eating other spiders. They will often shake the webs of neighboring spiders to trick them into thinking a tasty snack has been trapped. Instead, a fatal bite turns the host spider into the next meal. Funnel weaver spiders, hobo spiders, huntsmen, house spiders, and redback spiders are all favorites of the cellar spider. [Redbacks are related to black widow spiders.] This makes cellar spiders helpful in the house and the garden, reducing the number of potentially dangerous spiders. In a classic win-win situation, cellar spiders are “synanthropic”, meaning they benefit from living near us, too.
Members of the Pholcidae family, these arachnids go by several different names: carpenter spider, long daddy, marbled cellar spider, skull spider, vibrating spider, granddaddy longlegs, and daddy longlegs, hence the confusion.
Daddy longlegs have fatter bodies than cellar spiders, and they have a brown stripe on their belly. There are 6,000 to 10,000 species of daddy longlegs worldwide and they’ve been around for 400-million years, with very few changes. This group belongs to the Opiliones order. While Opiliones are arachnids, they are not spiders. The Arachnida class includes harvestmen, mites, scorpions, Solifugae (camel spiders), spiders, ticks, and may include horseshoe crabs. Scientists are still sorting that out.
True daddy longlegs are harvestmen, not spiders. They are most closely related to mites. If you were to compare cellar spiders with daddy longlegs, you would see that daddy longlegs have single eyes (or no eyes, depending on the species) and fused, pill-shaped bodies. They also differ in that they do not build webs, do not produce venom, and can eat chunks of food, as well as liquids. They defend themselves using stinky chemicals.
These creatures prefer hiding in moist areas, under logs and rocks, so you may find one under your kitchen sink or in a crawl space or basement.
Daddy longlegs are fascinating. They breathe using tracheae in their legs. And if one of those legs breaks off, as they too often do, it will continue to move because of a pacemaker mechanism found in each femur. This movement may continue for up to an hour. Scientists think this may have evolved to trick predators.
While daddy longlegs are predators in their own right, they get most of their nutrients from decomposing plant and animal matter, and manure. When they do hunt, they ambush their prey. This is impressive because their eyes cannot form images. [Don’t ask me. I have no idea how they do it.]
Daddy longlegs daddies are territorial and often care for the eggs laid by several different females, cleaning the eggs and protecting them from unrelated, egg-eating female daddy longlegs. [And we think our families are complicated!]
So, crane flies are pests, cellar spiders are helpful, and true daddy longlegs are pretty much neutral. Now you know.
Nodes and Internodes
Plant stems are divided into nodes and internodes.
Nodes are small knobby areas found on stems. You need to know about nodes when pruning and tree training. Internodes are the spaces between nodes and the length of internodes can tell you secrets about your plants
Nodes and leaves
Nodes produce buds, tendrils, and leaves. Sometimes those leaves have stems, called petioles. When identifying a plant, it helps to note if the leaves are arranged opposite each other, alternate up the stem, or are in a whorled pattern. Even if there are no leaves present, you can use the nodes and leaf scars to find the same information. Leaf scars are where petioles used to be attached. They look like tiny crescents. Whorled arrangements are a little trickier to identify without leaves because nodes can produce multiple leaves.
Aside from the normal stems we see coming out of the ground, there are also stems that run along the soil surface and underground stems. Aboveground modified stems can be crowns, spurs, or stolons. Stolons are often called runners, which is only partly true. All runners are stolons, but not all stolons are runners. Strawberries use runners to send out daughter plantlets that appear at each node.
Underground modified stems are bulbs, corms, rhizomes, and tubers. These underground stems are often mistaken for roots. If you can see buds, leaf scars, or nodes, it an underground stem. And each of those nodes can produce several buds. The eyes of a potato are nodes.
Nodes are important when it comes to pruning. It is just above a node where most cuts are made. To keep your plants healthy and productive, you want pruning cuts to be clean, smooth, and at a 45° angle, just above a node. You will also want to make sure that the node is pointing in the direction you want the new growth to go because it will. When you make this cut, all of the plant nutrients and hormones that had been directed toward continued stem growth will now be directed to the node, which will produce new growth. The same principles are applied when notching.
If you have a young fruit tree that isn’t putting out as many lateral branches as you would like, you can use notching. Notching is a method used two to three weeks before flowers appear to create a better structure. To notch a tree, first identify where branches are needed. Then, find nodes in those areas. Cut shallow notches one-third of the way around each branch, just above those nodes. By cutting through the phloem, the flow of auxins (growth hormones) will be redirected into the node, encouraging stem growth. Do not cut into the structural part of the branch. You should only notch a few nodes at a time, in case something goes wrong.
Plants use hormones, called gibberellins, to promote internode elongation, increase cell division, stimulate flower production, and regulate seed enzymes. Commercial growers apply gibberellins to plants to increase the size of Thompson seedless grapes, to end dormancy earlier than normal, and to force camellias to bloom out of season, among other things.
If you see internodes that are longer or shorter than normal for a plant at a specific stage of its growth, it can provide you with clues about its health. Shorter internodes can indicate low soil fertility. Longer internodes can mean the plant isn’t getting enough sunlight. This is called etiolation.
Take a closer look at the plants in your garden to see where the nodes are and how the length of the internodes change.
What’s happening at your plants’ nodes?
Each spring, buds burst forth with new leaves, flowers, and stems. But sometimes those buds appear in unusual places.
Normal stems produce one or more buds at nodes. Nodes are those small bumps you see along stems. The plant cells at nodes are different from plant cells elsewhere along the stem. Those cells are what make buds and leaves possible.
We expect to see terminal buds at the end of stems and axillary or lateral buds along the sides of a stem. This is where a leaf is already connected, on a shoot node at the leaf axil. These are normal ways of growing buds for vascular plants. But adventitious buds are rogues and outliers. This can be to their advantage. It can also be risky.
Adventitious buds turn up in strange places. You may find them along internodes, on leaves, in the callus of fresh pruning cuts, on new shoots, and even on roots. These buds are called adventitious because they take advantage of unusual opportunities.
In response to injury
When a plant is injured, whether through pruning, herbivore or insect feeding, fire, or mechanical injury, a whole slew of responses kick in to seal off the affected area. And sometimes the plant responds by trying to replace the damaged stems using adventitious buds. These buds may appear out from under the bark, at a pruning cut. They may pop up on the stump of a severed cactus.
As for the risks mentioned earlier, when a stem produces a lot of secondary growth, adventitious buds are often killed off. I have no idea who makes that decision or how it is carried out. I guess plants figure those outliers are expendable, as is often the case.
Which plants in your garden have adventitious buds?
Potato Mop Top
With a name like potato mop top, you know I had to dig deeper!
I immediately pictured the Beatles crossed with Mr. Potato Head. But it’s nothing like that. In fact, plants infected with potato mop top often look perfectly healthy. What’s strange about this viral infection is that it is spread by a different disease.
The powdery scab connection
You know how you are more likely to get a cold sore when you catch a cold? Well, plants infected with powdery scab become more vulnerable to the potato mop top virus (PMTV). Both diseases are caused by a Cercozoa [think amoebae] called Spongospora subterranea f. sp. subterranea.
Powdery scab is a slime mold that occurs in areas with poor drainage. When powdery scab is present, your potato plants are at higher risk of catching mop top. They can still be infected with PMVT without powdery scab, but the disease is less likely. Those that occur tend to be less damaging.
Potato mop top lifecycle
Potato mop top spores can remain viable in the soil for up to 18 years. All they need to become active is some moist weather, cool temperatures, and potatoes infected with powdery scab to work their way into tubers and the root system. From there, they move into the xylem and travel throughout the plant, blocking the flow of water and nutrient-rich sap. And potatoes aren’t the only garden plants susceptible to this disease. Your tomatoes and groundcherries may also become infected. Other nightshade family members and plants in the amaranth family, such as beets and spinach, may also become infected with potato mop top.
Potato mop top symptoms
Leaves of infected plants will show signs of yellowing, and the internodes will be shorter. Internodes are the spaces along a stem between two leaves, buds, or stems. This creates a stunted, “mop top” appearance. Foliar (leaf) symptoms can vary widely. Some potato varieties may exhibit a bright yellow blotch pattern (aucuba pattern) in the lower leaves, and others may have V-shaped yellow patterns.
Cut into a potato infected with mop top, and it becomes clear that something is wrong. You’ll see dark brown lines and spots throughout the tuber. Those symptoms are known as spraing. This damage looks similar to the alfalfa mosaic virus. You may also see deep cracks and skin distortions.
What’s strange about potato mop top is that plants grown from cuttings of infected plants may not show any aboveground symptoms but will have even more infected tubers than the parent plant.
Potato mop top management
The potato mop top virus is responsible for crop losses of up to 67%. There are no resistant varieties. Not yet, anyway, though russet-skinned potatoes seem to be less sensitive to PMTV. And there are no chemical treatments against viruses either. If a plant becomes infected with potato mop top, it must be removed and thrown in the trash. What’s worse, you can never grow potatoes in that soil again. Ever.
These good sanitation and vector controls are your only options when it comes to managing potato mop top:
As spring approaches, watch your potato patch begin to wake up from its winter sleep. As new shoots appear, monitor for signs of this and other diseases so you can nip them in the proverbial bud.
Potato Virus X
Symptoms of potato virus X
You may not see symptoms other than a drop in tuber production. Your plants may look bushier. Or, you may see chlorosis, dead spots in tubers, leaf crinkling, mosaics, ringspot, and smaller leaves.
Potato virus X management
Potato X disease is spread mechanically on tools, clothing, and infected roots and tubers. Avoid walking through potentially infected areas and use clean, disease-free seed potatoes to prevent this disease. Crop rotation can help break the cycle once it occurs.
Since potato X also appears on weeds in the same families, pull any bindweed growing near susceptible crops. Heck, it’s always a good idea to get rid of bindweed.
Some potato varieties, such as Atlantic, HiLite Russet, Norwis, and Sebago, are somewhat resistant to PVX, so you may want to use them in your potato patch.
No, potato leafroll is not a starchy new snack.
Potato leafroll, also known as potato leaf curl virus (PLCV), is a viral disease spread by aphids. This disease predominantly affects the vascular tissue of potato plants. The potato leafroll virus (Rhizoctonia solani) causes up to 50% of potato losses worldwide. That works out to about 20 million tons of lost potatoes each year.
Potato leafroll symptoms
Potato leafroll affects plants in two waves of infection. The first wave is recognized by leaves curling upwards, yellowing, and brown leaf edges. These symptoms are often seen first on the lower leaves of plants infected the previous season. Plants infected during the current season are the opposite, with symptoms occurring first on younger leaves.
The second wave is more severe. Entire leaves can become chlorotic and may develop purplish or reddish margins. Eventually, infected leaves dry out completely, plants become severely stunted, and smaller tubers are produced. Symptoms may also be seen in the phloem of the haulm or stem. You might also see something called net necrosis. Net necrosis appears as small brown strands or speckles of discolored tissue that start at the tuber’s stem end and move through the tuber. Net necrosis may be confused with zebra chip.
Potato leafroll infects other plants, too, with slightly different symptoms. You might see interveinal necrosis [dying veins] and curled, leathery leaves in infected golden pearls (Solanum villosum), moonflowers (Ipomoea alba), and thorn apples (Datura stramonium). Groundcherries and tomatillos infected with PLRV exhibit chlorosis, leafroll, and stunting. Weeds in the nightshade family can also contract and harbor this disease.
Potato leafroll looks a lot like stem end discoloration, a physiological disorder believed to be caused by too much heat, cold, or frost. PLRV may also be confused with early signs of Rhizoctonia stem canker and black scurf.
The potato leafroll virus is spread by several types of aphids, with green peach aphids (Myzus persicae) being the most destructive. When an aphid feeds on an infected plant, the virus enters the aphid’s gut and starts reproducing. From there, the virus floats around in the aphid’s circulatory system until it reaches the salivary glands. Then, when the aphid pierces the leaf of a healthy plant to feed, the virus is spread through the saliva into the phloem of the new host. Once an aphid has become a carrier, it stays that way, potentially infecting dozens of plants.
How to prevent PLCV
Aphid control is the first line of defense against potato leafroll. As any gardener knows, controlling aphids is a battle of epic proportions that never ends. Insecticidal soap is probably your best aphid treatment. [Do not use dish soap or other types of detergent, no matter how many people say otherwise.]
In some cases, infected seed potatoes (and grocery store potatoes) can carry this disease, so always plant certified disease-free seed potatoes. Sadly, seed potatoes sold at many garden centers are infected with the potato leafroll virus and aphid eggs. It pays off to be picky when shopping for seed potatoes or any other plant material. And never add grocery store produce to your garden. It can carry many pathogens.
Also, keep weeds from the nightshade family away from your potato crop. This group includes bull nettle, horse nettle, and creeping wolfberry. Mustard and shepherd’s purse can also harbor this disease.
If you find an infected plant, remove it and three other plants in each direction and throw them in the trash. Just to be sure.
For decades, I thought the lyrics were “oak salad” but the distinct downbeat and thumping bass of Tony Joe White’s Poke Sallet Annie tells a gardening story that makes you wonder how people ever started eating this poisonous plant. But eat and grow it they do!
[I urge you to click on the link above to listen to the song as you read – it’s a classic and it’ll get you moving for sure!]
Poke sallet (Phytolacca americana), also known as inkberry, pokeberry, pidgeonberry, and pokeweed, is a perennial weed that is native to eastern North America, the Gulf Coast, the Midwest, but is now found along the California coast and is appearing throughout North America.
The poke sallet plant
Poke sallet is described as something like turnip greens. Being able to grow 10’ tall, I’d have to say that was one heck of a turnip! Instead of a bulbous root, poke sallet plants have taproots from which multiple sturdy green, crimson, or purplish branches grow. Smooth-edged, spade-shaped leaves can be 16” long and often have a funky smell. Sometimes leaf veins are crimson, too. Small, white to pinkish-white flowers grow in elongated clusters called racemes. These flowers are unique in that they do not have petals. Instead, they have five upright sepals. These sepals start to droop as the fruit develops. Berries are a glossy purplish-black.
This plant dies back each winter and returns each spring. Also, seeds can remain viable in the soil for up to 50 years. If you don’t want poke sallet in your landscape, you’d best remove it before it goes to seed.
Poke sallet is poisonous to people, dogs, and livestock. The berries and roots are extremely toxic, getting more so as the plant ages. But local birds, giant leopard moth caterpillars, gray and red foxes, opossums, raccoons, and white-footed mice love the berries and are not affected by the toxins.
Before you try harvesting (or removing) some poke, you need to know that pokeweed sap can be absorbed through the skin and should be avoided. Historically, poke sallet was used to treat arthritis. The plant was also mistaken for horseradish, Jerusalem artichoke, and parsnip. In the 1890s, poke sallet extract was even advertised as a weight-loss cure. As a result, poisoning was common. That being said, in her memoir, Dolly Parton admitted to using poke sallet berry juice as a lipstick, when her parents forbade her from wearing makeup.
How people decided to eat poke sallet is beyond me. It ends up that new shoots and leaves can be eaten, but only if prepared in the right way. [I have always wondered about all the times people kept trying to find the Right Way by learning they had discovered yet another Wrong Way. How many times do you keep trying? I know hunger can certainly be a powerful motivator, but damn!] When prepared as food, the tender new leaves and shoots are often called poke salad or polk salad. When not prepared properly, poke sallet can cause explosive digestive problems and even death.
The proper method of preparing poke sallet involves boiling young leaves and stems two or three times in fresh water, for 20 minutes each time. Poke sallet greens are then fried in bacon grease and seasoned with salt and pepper. Onions may also be added. The stems are said to taste like asparagus, while the leaves taste like spinach.
I don’t know if I will consider poke sallet a garden edible or a weed. I guess it’s both. But I probably won’t be ordering seeds any time soon.
Would you eat poke sallet if you found it growing in your landscape?
Sweet Potato Scurf
Sweet potatoes can be grown in large containers and look lovely on a patio.
And, sometimes, they get sick with a fungal disease called sweet potato scurf.
Lush aboveground growth of your sweet potato plant may give no sign of diseases at first. But if you dug up a portion of the root system, you would see discolored areas of various sizes and shapes. These superficial lesions are gray on yellow-fleshed sweet potatoes and purple, brown, or black on orange-fleshed varieties. These discolorations look similar to black scurf and silver scurf of regular potatoes. Unlike silver scurf, sweet potato scurf does not penetrate beyond the skin. Eventually, these lesions can be seen on the stems and leaves of heavily infected plants.
While sweet potato scurf (or soil stain) doesn’t look too terrible and can be scraped off, these fungal infections make it more likely that other diseases and pests will get in. In storage, infected sweet potatoes dry out faster.
Humidity is necessary for sweet potato scurf to develop. It often appears during the rainy season. And it is more likely to occur in areas with heavy soil, after top dressing with a lot of manure, or in soil with high levels of organic matter. Organic matter usually helps plants grow better. Apparently, sweet potatoes stay healthier when grown in light, sandy soils.
Sweet potato scurf management
Sweet potato scurf is caused by the Monilochaetes infuscans fungi. This isn’t a resilient soil-borne fungus. Without a host, it generally only survives for 1–3 years in the soil, depending on the soil type. This makes crop rotation a very effective control. In areas where sweet potato scurf has been a problem, growers generally rotate crops every three or four years.
Spores can be spread via tools, clothing, baskets, and shoes, but infected plant material is the primary culprit. This means you can often avoid it by only planting certified disease-free slips. Slips are baby sweet potato vine cuttings used to make new plants. Commercial growers treat slips with fungicide before planting as a preventative measure. There are no fungicides that control the disease once it takes hold.
When you buy seeds or seedlings, you may see the letters “OP” somewhere on the label. These letters stand for “open-pollination” and they tell you something about the family history of that particular plant.
Until the turn of the twentieth century, all of your garden plants were open-pollinated. By 1969, 71% of the U.S. corn crop was grown from hybrid seeds. This isn’t a judgment call – we have a lot of people to feed. But there are differences.
Pollen and parentage
Pollen provides half the genetic information contained in a seed. Plant ovaries contain the other half. The way that pollen gets from the male flower to the pistil, or female parts, determines if it is an heirloom, hybrid, or open-pollinated.
Hybrids and heirlooms rely on human intervention to achieve whatever results are desired. Those results may be disease resistance, heavy production, or protecting a piece of history. Hybrids are developed on purpose to take advantage of the best characteristics of both parents. They tend to be far more fertile and productive than non-hybrids. Heirlooms and hybrids are often grown for seed in protected areas, such as greenhouses, to ensure that the genetic information stays true to the original.
Open-pollinated seeds throw caution to the wind. They are the wild side of seed production.
What is open-pollination?
Open-pollinated crops use natural mechanisms to spread pollen. This means self-pollination is a type of open-pollination. It also means wind, bees and other insects, birds, bats, your jacket, and anything else that comes into contact with the stamen, or male parts of a flower, may be used as a vehicle. This introduces a lot of genetic diversity into the mix.
Genetic diversity and plant health
Many heirloom crops have evolved, over countless generations, with natural resistance to many pests and diseases. They had to so that they could live long enough to reproduce. Mass-produced, monoculture hybrid crops are extremely productive. They are also very susceptible to pest and disease attacks. And, as we have all learned recently, a single virus can wreak havoc on a population.
Open-pollination leaves the door open to greater genetic diversity. This often results in improved species health, insect resilience, and disease resistance. It can also create entirely new varieties.
Seed saving isn’t helpful to gardeners if the resulting offspring are not edible or useful in some other way. If seeds produce offspring that are consistently identical to their parent plants, we say that they “breed true” or that they are a “standard variety”. These are seeds that can be relied upon to produce what you expect them to. Most open-pollinated and heirloom seeds breed true, but not always. Seeds produced by hybrids do not breed true and must be repurchased each year.
If you are a commercial grower in need of consistent timing, plant size, and treatment needs, hybrids are the way to go. You know what to expect and how to respond. If you are a home gardener, you are free to take things more casually.
For example, if you have a favorite tomato plant and you want seeds that breed true, you will need to protect that plant from the pollen of other tomato varieties. This can be done by planting different varieties at different times, making it so flowers are not blooming at the same time. You can isolate your tomato plant in a greenhouse or under a cover and hand-pollinate. Or, you can put distance between it and other tomato varieties.
The distance needed to prevent cross-pollinating with other species depends on the mating system of a species. You can separate your modern tomato and most self-pollinating plants by 10’ or you can put miles between your spinach plants.
Yes. Wind-pollinated crops, such as spinach and beets, produce pollen that can can fly on the lightest breeze for miles. Insect-pollinated crops require a wide range of isolation distances. The Seed Savers Exchange offers an excellent resource for isolation distances. Honestly though, most of those distances are more than we can manage in our yards. Lettuces and that prize tomato may only need 10’, but most vegetables need at least 1600’, but even that is no guarantee. If you really, really want seeds that breed true, you may have to grow only that variety and no others.
So, next time you go shopping for seeds, will you look for hybrids, heirlooms, or open-pollinated seeds? Why is that choice better for your garden?
Long hours, social isolation, and tons of uncertainty can make any of us testy. Testae have nothing to do with any of that. This post is about seeds.
If you pick up a seed, the first thing you’ll see is its testa. Testae are the outer coverings of seeds. Tucked safely inside are the embryonic plant and its food supply.
Also known as husks, hulls, and seed coats, most testae look pretty boring at first glance. They tend to be smooth, hard, and simple. This is not always the case. There are winged seed coats, hairy seed coats, and even seed coats with prickles!
Seed coats start out as the maternal material that surrounds ovules. Put simply, ovules are a plant’s eggs. So, I suppose we could say a testa starts out as the thin film found between the shell and the hardboiled egg you peeled not too long ago. In both cases, that material is called an integument. Integuments are neutral outer coverings, such as skin and rinds.
Did you know that hen’s eggs have two layers of protective membranes under the shell? There’s a third membrane around the yolk, but we can skip that one for now. It’s those membranes that make it easy (or difficult) to peel your snack. [Note: fresh eggs are harder to peel. If you start them cooking in hot water, rather than cold, they will be a little easier to peel.]
Types of testae
Seed hulls can be hard and rugged, as in the case of coconuts, or they can be extremely thin and delicate, as with the filmy covering over each pomegranate seed (sarcotesta). Botanically, there are two types of seed testae: bitegmic and unitegmic. [From the Latin tegō for "I cover"). Bitegmic seeds have testae made from two layers, while unitegmic testae are made from one.
Parts of a seed coat
It takes several layers of integuments to make a seed coat. These layers are first classified as inner and outer. If you want to dive deep down this rabbit hole, I suggest taking a look at Radchuk and Borisjuks’ Physical, metabolic and developmental functions of the seed coat. For the sake of today’s discussion, suffice it to say that these layers do everything from producing pigments, protective cuticles, and even toxic chemicals, all to improve a seed’s chance at survival.
We all know that the primary function of a seed coat is protection. Hulls prevent mechanical injury. They keep seed contents from drying out and they prevent pests and pathogens from getting inside. But testae also prevent germination.
If a seed germinates too early or too late in the growing season, it usually dies. The seed coat prevents this from happening by blocking air and water from getting in, creating a forced dormancy. But how does a seed know when to germinate with all this protection?
Seed coat dormancy
It ends up that seed coats pass on information about environmental conditions to the embryo. Until conditions of humidity and temperature, and sometimes light, are right, the seed coat battens down all the hatches, creating a self-imposed dormancy. During seed coat dormancy, not even air and water can get through. Of course, insects, microbes, erosion, and passing through a digestive system can wear a seed coat down. When we damage the seed coat on purpose, we break that barrier. This is called scarification. Also, testae have holes in them, called micropyles. These holes are how pollen tubes get inside for pollination.
Either by choice or by outside influences, eventually, the seed coat stops protecting its charge, allowing water and air to start seeping in. This is when germination begins and the life of a seed coat ends.
Starting seeds is a garden rite of spring (and other seasons), but you might not know where to start.
Do your seeds need to be soaked? Stratified? Or, scarified? Let’s find out.
Most seeds are surrounded by a hard hull or seed coat. The seed coat protects the embryonic seedling and its food supply (endosperm) from moisture, pests, and disease. Rising temperatures and spring rains soften the seed coat, allowing moisture to enter and triggering the new plant into reaching for the sun. Before they do that, many seeds need to go through a period of winter rest before they can successfully sprout in spring. Some seeds, such as lettuce and dandelions, have evolved to be blown on the wind, landing lightly where they fall, while others need to be buried deeply in cold, damp soil – think acorns and squirrels.
If you plant a seed before it gets warm enough outside, odds are pretty high that the seed will either rot in the ground, or it will never really thrive. Understanding each plant’s unique ideal sprouting and growing conditions will help you start seeds more successfully.
Most garden seeds will germinate when temperatures reach 60°F to 70°F if they are planted in loose, moist soil at the proper depth. The general rule of thumb for seed planting depth is to use twice the seed width or diameter. This means a seed that is ¼” wide should be planted ½” deep. Too often, seed packets rely on a standard planting depth, which is not always in a seed’s best interest. If you will be planting a lot of seeds, you may want a dibble.
Okra, pumpkin, and squash seeds need a lot of heat (85°F to 95°F) to have a good start. This group is followed closely by beans, eggplants, and watermelons (75°F to 85F). [You can email me for a free chart of ideal temperatures for germination.]
This group needs to be covered with soil, but only a little. It includes broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, collards, cucumbers, eggplant, kale, kohlrabi, leeks, melons, peppers, squash, and tomatoes.
Seeds to soak
Some seeds are more likely to germinate and grow well if they are soaked overnight before planting. This group includes asparagus, beans, beets, carrots, corn, okra, parsley, peas, pumpkins, squash, and Swiss chard. Do not soak seeds for more than 24 hours or they will rot.
Seeds to scratch
Some seeds have evolved for a more rugged life. Often, these are seeds that, in nature, end up going through someone’s digestive tract before being deposited on the ground with a convenient pile of fertilizer. If you scratch or nick the surface of your bean, melon, and squash seeds, and then soak them overnight, you can significantly increase germination rates. Just be sure that you do not puncture the seed coat as this can kill the embryonic plant. Just rough it up a little. This is called scarification.
Once your seeds germinate and start to outgrow their first home, you will need to transplant them. Transplanting is extremely stressful. Root hairs get torn away, everything starts drying out, and getting reestablished takes time. Some plants really hate being transplanted. This group should be planted directly where you want them to grow, if at all possible, and it includes anise, arugula, borage, carrots, chervil, cilantro, dill, fennel, mustard, parsley, parsnips, peas, radish, rutabaga, spinach, Swiss chard, and turnips.
Other plants, such as beans, corn, cucumbers, melons, and squash, grow so quickly that it’s just easier to plant them where you want them.
If you start your seeds indoors or in an otherwise protected area, you will need to harden off seedlings. Hardening off refers to gradual exposure to the sun, wind, and various temperatures. Plants don’t take kindly to shocks.
Use these tips to get the most out of your seed planting efforts:
What seeds are you starting?
Growing Food Indoors
Not everyone has a yard, but that doesn’t mean they can’t grow edible plants.
Today we are looking at several vegetables and herbs you can grow indoors.
You may be surprised to learn that 43% of American agricultural crops are grown under protection. Under protection can mean in a greenhouse or hoop tunnel, but it’s not that much different from your living room, if you have enough sunlight.
Before we look at specific plants, let’s consider the particulars of growing indoors:
Now for the list of edible plants that you can grow indoors!
Carrots grow well in containers. They are not very competitive and are easily discouraged by rocks and compacted soil. Cover seeds only lightly with soil. Mist them each day to keep the seeds moist until they germinate. Your carrot tops will make nice houseplants and can be used repeatedly to make new carrots.
In the same way, you can use the base of a celery plant repeatedly for stalks. Just keep in mind that your homegrown celery may not look like the thick, straight stalks you see in the grocery store. If you want them to look like that, you have to put in a little extra effort. See my post on celery for more information about that.
While bell peppers are best left outdoors, you can grow smaller chili peppers indoors. These attractive plants need a lot of heat and sunlight to produce fruit. While most pepper plants are self-pollinating, you can increase your crop size by hand-pollinating, or just giving your pepper plants a gentle shake every now and then.
Many herbs prefer the outdoor life, but you can still grow chervil, chives, cilantro, ginger, lemon balm, lemongrass, marjoram, mints, oregano, parsley, rosemary, sage, tarragon, thyme , and turmeric indoors. Most of these herbs need at least 5–6 hours of sunlight each day. Basil can be grown indoors, but it needs more sunlight than that.
Alfalfa sprouts aren’t the only microgreens you can grow at home. Sprouts are nice additions to salads and sandwiches, and they require little to no soil to grow. You can use a sprouting jar or a shallow tray filled with moist potting soil. Arugula, basil, beet, chard, cilantro, kale, and radish are just a few plants you can grow as microgreens. [Do not use members of the nightshade family in this project as the seedlings can be poisonous.]
If you’ve never tried one of those mushroom growing kits, I urge you to give it a go. It’s amazing to watch and the mushrooms are delicious. No sunlight is required.
Your indoor pea plants will climb whatever they can get their little tendrils around and you can use that to your (and their) advantage. Put something they can climb in front of a window. Before you know it, you can be harvesting sweet, fresh peas.
With just a little space and light and you can have fresh radishes year-round. And the nice thing is, you are not limited to the traditional red globes of your childhood. Radishes now come in a variety of shapes, sizes, and colors. And they still germinate in only a few days.
Add some strawberry crowns to an indoor planter and watch as the magic happens. You will need to hand-pollinate your strawberries, but you won’t have to fight with slugs and snails!
Ah, tomatoes. The joy of every gardener. Your indoor tomatoes will require lots of light and hand-pollinating, but they are worth it. And a staked cherry tomato plant is a sight to see (and eat)!
Other crops that can, with enough sunlight and space, be grown indoors include cauliflower, cucumbers, potatoes, and sweet potatoes. Before taking on these trickier behemoths, start with something smaller and simpler to see how it all works. Remember that temperature and humidity have a big impact on plant health. Also, plants tend to grow more slowly indoors.
While I normally urge everyone to avoid planting grocery store produce, due to the potential of pests and diseases, this case is different. These plants will all be growing in containers. If there is a problem, it is limited to that container (unless it’s aphids or fungus gnats). Worst case scenario, you throw the whole thing in the trash and start over. Growing these edible plants indoors, it is easy to start with the base of store-bought celery or scallions or the tops of grocery store carrots.
Finally, to keep your indoor plants healthy and productive, you may want to turn a fan on them once in a while. Plants need the stimulation of touch to grow well. This is called thigmomorphogenesis. [How’s that for a cool garden word?]
What edible plants are growing in your house?
We’ve all ended up with packets of seeds from previous years. Are those seeds any good? Even if they sprout, will they grow into healthy, productive plants?
How long do seeds last, anyway?
I am asked that question every spring. And every spring I tell people, “It depends.”
The answer comes down to viability and vigor.
Seed viability refers to a seed’s ability to germinate under normal conditions. Seed vigor is all about that seed’s ability to successfully grow into a mature plant. The likelihood of a seed being able to germinate coming out of storage depends on the type of plant and the way it was stored. But start by looking at the seed packet.
If you look at a seed packet, you may see a “packed for” date. You may also see a “sow by” date. The “packed for” date tells you the year the seeds were produced and packaged. The “sow by” date tells you the point at which seeds will be less likely to produce strong, vital plants.
Seeds may not look like anything exciting is going on, but they are alive. They are eating and breathing embryonic plants. They just do those things very slowly. Stored starches (endosperm) are consumed and gas exchanges still occur. It isn’t until the seed hull is softened by moisture and heat that the exciting business of germination begins. But how can you help your seeds survive being held in storage and how can you tell if they are any good?
1.Wet a paper towel or paper coffee filter and squeeze out as much water as you can.
2.Place up to 10 seeds on the paper towel.
3.Roll it up or fold it and put it in a sealable bag or plastic container.
4.Be sure to attach a note that includes the plant type, the date the test started, and the average days until germination from the seed packet.
5.Place the bag in a safe, warm spot, above 70F°.
6.Mist as needed to maintain humidity without getting soggy.
7.After one week, check the seeds every day for signs of germination.
Note that some seeds need light to germinate. This group includes chamomile, lemon balm, lettuce, and savory. You can conduct the same test with these seeds, simply leave the paper towel flat, exposing the seeds to light.
If you test 10 seeds and 7 of them germinate, you will know that they have a 70% germination rate. Generally speaking, germination rates below 70% are not worth planting. Also, this won’t tell you if those seeds have the energy they need to thrive, but you will at least know what to expect in the germination department. And those germinated seeds can be gently planted in soil. Don’t worry if some of the paper is attached. It’ll disappear on its own before you know it.
In fact, you can make planting easy by tearing paper towels into strips and putting drops of non-toxic glue at the proper intervals. Then pour seeds over the strips (in a big container so you don’t lose seeds), give the strips a shake, and lay them flat to dry. Be sure to write the seed type on the paper towel. This works especially well with tiny lettuce seeds that are scattered on the soil surface. The paper toweling holds them in place long enough to start growing, but the glue and paper towel decompose into the soil. This is a fun kids’ activity, too.
Not all seeds will sprout well in a damp paper towel. Peanuts and Malabar spinach, for example, need soil. For these seeds, use a tray filled with wet potting soil. Cover the seeds with vermiculite to help maintain moisture levels. Keep the soil warm and moist. Seeds should germinate in 7–10 days.
Instead of letting seeds die of old age and neglect, take some time to go through your seeds and plant them sooner, rather than later.
This year, I’ve decided to plant every seed I own. I have to stay home anyway, being low on the vaccine list, so it seems like the perfect time. Plus, two friends have given me all their canning equipment!
It’s going to be a busy summer…
If I had a nickel for every time something went wrong in the garden…
But, wait! The truth is, if I had a nickel for every time something went well in the garden, well, I’d be a rich woman.
Talking about nickels, did you know that nickel is a plant nutrient? Let’s find out what it does.
Most of us who play in the garden are familiar with the Big Three of plant nutrition: nitrogen, phosphorus, and potassium. These are the NPK of fertilizer fame, respectively. They are called macronutrients because plants use them in relatively large quantities. You might consider them the meat and potatoes of a plant’s diet. Following the macronutrients in quantity consumed and importance to plant health are the secondary nutrients of calcium, magnesium, and sulfur. These are the side dishes.
Just as any meal would be bland and unsatisfying without seasonings and little surprises, a plant’s diet must also include several micronutrients: boron, chlorine, cobalt, copper, iron, manganese, molybdenum, selenium, silicon, sodium, vanadium, zinc, and nickel.
Now, nickel (Ni) wasn’t recognized as a plant nutrient until late in the game. In 1987, one group tried to sponsor nickel into the plant food arena, but it wasn’t until 2004 that the American Association of Plant Food Control recognized nickel as an essential element. [I’ll bet you didn’t know that was a group – I sure didn’t.] It ends up that nickel is used in such small quantities that we didn’t have the technology to measure it properly until the mid-1970s. California still refuses to acknowledge nickel as a plant nutrient. I have no idea why.
Orders of plants
Before we learn how plants use nickel, we need to understand the difference between higher and lower order plants. Lower-order plants do not have vascular bundles. These are the algae, hornworts, liverworts, and mosses. Higher-order plants have veins. This ginormous group includes ferns, gymnosperms (including conifers), and flowering plants (angiosperms). Now that we’ve cleared that up, we can learn how they use nickel.
How plants use nickel
In vascular plants, nickel is an extremely important puzzle piece that unlocks the ability to metabolize and fix nitrogen. It is also used to help plants process urea. Urea is commonly used as a source of nitrogen. Too much urea in a plant can cause necrotic lesions [read ugly, weeping sores]. Nickel helps convert urea into ammonia (NH3), which plants can then use as a nitrogen source.
In lower order plants, nickel is used to activate enzymes in several different processes. These more primitive plants can often use nickel in place of iron and zinc.
In legumes, nickel is a major player in the development of root nodules used to fix atmospheric nitrogen into a form plants can use. Nickel is also very important to pecan trees. And plants are more likely to get sick when they don’t have enough nickel.
Speaking of plant diseases, nickel has been found to help prevent several of them. Scientists aren’t sure if this is because nickel stimulates the plant to defend itself or if the nickel acts directly on the pathogen, but it is important. Research has found that nickel applications reduced cowpea fungal diseases of leaves by 50%. That’s huge!
Signs of nickel deficiency
Leaf tip death is the earliest sign of a nickel deficiency. Nickel-deficient pecan trees develop “mouse-eared” leaves, bud break is delayed, and bronzing, chlorosis and leaf tip death are common. [Mouse-eared leaves are smaller than normal and curled.]
This damage can be reversed with the application of a dilute nickel solution. Before you go around painting leaves with nickel water, you need to know that these deficiencies are extremely rare. So rare, in fact, that nickel isn’t included in most soil tests (unless you want to pay extra). That being said, soils low in nickel can be found in the southeastern United States and parts of England. These soils also tend to be low in manganese and zinc. Adding nickel in these cases has been shown to significantly improve bean, potato, and wheat crops.
Nickel is a mobile plant nutrient, which means it moves around within the plant freely, going to wherever it is needed.
There you have it. You now know more about nickel in plants than pretty much everyone you know.
Some garden words just beg to be written about. Black scurf strikes me as one of those.
Black scurf is a fungal disease of potatoes most easily recognized by lots of small, irregular, dark bumps on your potato skins. These bumps look like soil but they don’t wipe off. There is also a silver scurf of potatoes and a different type that infects sweet potatoes. We will discuss those some other time.
Black scurf is caused by Rhizoctonia solani. This is the same fungus that causes belly rot, collar rot, damping off, Rhizoctonia blight, root rot, and several turfgrass diseases. Black scurf is mostly cosmetic if you’re talking about the edibility of a potato. This disease will reduce your crop size, weaken any plants that survive, and may kill off your seed potatoes.
If you’ve never grown potatoes, it helps to know that they are grown from seed potatoes. Seed potatoes are not seeds. They are simply potatoes, or pieces of potatoes, that have at least one of those “eyes” that sprout in your refrigerator or pantry. When you plant those pieces of potato, you put them in a trench that is 6–8” deep, with the cut side down and the eye pointing up. Those raw edges and new growing tips are vulnerable to several types of attack, including black scurf infections.
Symptoms of black scurf
The tell-tale dark bumps seen on potatoes infected with black scurf are clusters of resting fungal mycelium known as sclerotia. These sclerotia do not damage the still-edible potato, but they do perpetuate the disease. As temperatures rise, these sclerotia germinate. The mycelium may begin growing again, too.
As the disease progresses, you may also see reddish-brown lesions on stolons, stems, and roots. When the lesions move to above ground stems, the disease becomes known as Rhizoctonia canker. These lesions mature into rough, brown cankers that can girdle the stem, killing everything above it.
If a black scurf infection hits critical mass and starts its sexual phase, you may also see a white, powdery mold just above the soil line. This is especially common after it rains or been foggy. Heavily infected seed potatoes are unable to produce stems, in a condition known as “no top”.
Black scurf look-alikes
Diagnosing plant disease can be tricky, especially when you’re new to gardening. I like to look at it as a puzzle, searching for clues. In the case of black scurf, there are a few other diseases that look similar enough to warrant closer inspection. If stems look mushy, it’s probably blackleg. If seed potatoes rot in the ground, it’s probably caused by Fusarium. If you notice leaf curl, the potato leaf curl virus may be causing the problem.
Sadly, you often won’t see signs of this disease until later in the season, long after the damage is done. If your potato crop is mostly small, green tubers (aerial tubers), it’s probably black scurf. This occurs because the invading fungi interrupt the flow of nutrients through the vascular bundles, making life difficult for your potato plants.
Black scurf control
Since many soil-borne disease fungi seem to be able to hang in limbo for years, preventing disease ends up being easier than curing it. Some people suggest a 3-year crop rotation but this is only marginally effective. Those years mean nothing to resting fungi, but it can’t hurt.
Commercial potato growers use fungicides containing chemicals with names like azoxystrobin, flutolanil, and mancozeb to treat black scurf. These chemicals range in side effects from mild skin and eye irritation to bird toxin to a possible carcinogen, respectively. I don’t want any of them in my garden or my food. Instead, there are other ways to prevent black scurf from infecting your potato crop.
The easiest way to prevent black scurf is to only use certified disease-free seed potatoes. Seriously. As tempting as it may be to plant those refrigerator/pantry sprouts, don’t do it. Those potatoes can carry potato blight, the disease responsible for Ireland’s Great Potato Famine, along with several other difficult to get rid of diseases. Buying healthy seed potatoes is a small price to pay. Plus, once you start your potato bed, it can go on forever.
When planting, wait until soil temperatures reach at least 60°F. This gives your seed potatoes a better shot at being healthy and strong enough to protect themselves. Also, Rhizoctonia does not compete well with other soil microorganisms, so maintain plenty of organic matter in the soil to improve overall soil health and microorganism populations. As always, avoid overhead watering, space your plants out with an eye to good airflow, and dispose of infected plants in the trash.
Researchers have found that mulching your potato bed with a green manure made from members of the cabbage family helps prevent black scurf (Sexton et al., 2007). Apparently, compounds released by the Brassicas actively kill the sclerotia. Unfortunately, both potatoes and Brassicas host white mold. If white mold is a problem in your garden, you may want to avoid that particular treatment.
Harvesting your potatoes as soon as they are mature also reduces the chance of infection, along with bruising and insect damage.
Potatoes are an easy crop to grow. They look great in towers, containers, and raised beds. And, like their near-sibling, the tomato, fresh is far better than store-bought.
You can grow a surprising amount of food in your own yard. Ask me how!
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