Pets, Pests & Problems
Pest Control: General Guidelines
The principles that guide organic pest-control are simple: try to make the lawn unattractive to pests and attractive to beneficial plants, animals, and insects. Wonderful ideas; the dilemma is, how to put them into practice without going back to school for four years for a combined degree in soil science and entomology.
Fortunately that won’t be necessary. The simplest way to control lawn and landscape problems of any kind (insects, weeds, fungi) is to grow a healthy lawn. That may sound too easy, but it’s true. You’ll never eliminate all the harmful weeds and bacteria and insects from your lawn any more than you’ll eliminate ALL the disease-bearing bacteria from your home. The goal is for you and your yard to be healthy enough so that the ones that are around can’t make either of you sick.
So don’t give pests an opportunity. Make sure your lawn is properly watered and your grass is growing in good, healthy soil. Choose grass that will grow well in your climate — that alone will make your lawn more pest resistant than trying to grow a water-hungry variety in a water-starved area like parts of Arizona, New Mexico or Nevada.
Maintaining a healthy lawn does an enormous amount in itself to attract beneficial organisms and hold harmful ones in check. A healthy organic lawn encourages earthworms, micro-organisms, butterflies, and the lacewings, ladybugs, and other insects that eat lawn and garden pests. A thick lawn doesn’t have many spaces in which weeds can establish themselves, and it’s generally able to beat back incursions from the fungi that always exist in the soil — just as a healthy person doesn’t get a cold every week of the year, even though cold-causing viruses are always around.
If your lawn does get some sort of infestation or disease, consider what it is and why it finds your yard such a nice place to hang out. Repeated visits from moles or other tunneling creatures suggest that they’re finding plenty of grubs in your grass. They’re certainly eating something; they wouldn’t bother to come by otherwise. Get rid of the grubs, and the moles will go elsewhere.
Unfortunately, moles themselves aren’t considered a viable grub-management tool, and once you dispense with the moles, you still have the grubs to deal with. These short, fat, white, worm-like things (beetle larvae which dine on grass roots) turn many a human stomach, but birds consider them a delicacy. So encourage birds to drop in and dine by putting out a bird-bath and changing the water on a regular basis.
In the first instance, you make the yard unattractive to moles by removing their food supply; in the second case, you make the lawn attractive to birds, a grub predator.
Ironically, synthetic insecticides can sometimes bring on a pest infestation, because most are indiscriminate. They kill off everything, including the beneficial bugs that would prey on the pests you want to get rid of. If you want to make your yard attractive to beneficial insects, you’ll need to avoid killing them.
Here’s an overview of natural pest control techniques:
For diseases: Many diseases thrive in thatch; make your lawn less attractive to them by removing the thatch layer.
Many fungi (the cause of most lawn diseases) get a foothold when a lawn is either over- or under-watered. Maintain steady, adequate moisture to keep diseases at bay.
For insects: Again, keep thatch under control.
Pick bugs off your lawn by hand. Obviously this will work only with a small infestation of large bugs, but it’s often worth trying before you reach for a big insecticidal gun.
Natural pest repellents such as garlic and pepper sprays will repel many insects. Combine the repellent with water in the blender and then strain out the fiber. Or use insecticidal soap, effective against many problematic insects.
Traps, which allow the pest to “check in but not check out” can effectively control wasps and a number of other pests. Put insect traps on the periphery of your lawn so the pests will be disarmed before — rather than after — they dine on your tasty lawn, flowers and shrubbery.
For caterpillars: Try Bacillus Thuringiensis (BT), a bacteria that affects only moth and butterfly larvae — most caterpillars. If a caterpillar ingests BT and then gets eaten by another bug or a bird, the bird will not be harmed. This bacteria does not move up the food chain, and it does not affect earthworms.
For beetles and other insects with shells: Try diatomaceous earth, a fine silica powder made from the fossilized shells of already minute creatures called diatoms. The razor sharp powder destroys the shells of crawling insects, but does not harm earthworms, pets, or humans. Different bugs are susceptible to different extents (even beetles differ somewhat), so check before buying.
For insects and diseases: Prune diseased leaves, branches or whole plants in your garden, and remove them from the garden entirely, so that problems don’t migrate from them to the lawn. Keep things tidy. This will help to limit the spread of disease.
For weeds: In spring or fall, use corn gluten, a pre-emergent herbicide (meaning that it kills seeds) and as a bonus, an excellent nitrogen fertilizer for grass. There are also a number of effective organic herbicides based on citrus or clove oils. Unfortunately, they’ll kill anything they touch, so they need to be applied with care.
Weeds need bare ground and sunlight to get established; thick grass deprives them of both.
Bugs & Other Thugs
If you do want to attract insects to your lawn, here’s how you can do it. Cut the grass short so it stays constantly weak. Fertilize with quick-release chemicals that force soft topgrowth to develop without equal root growth to support it. Water lightly and often. Keep the top of the soil wet, but allow the root area to dry up. Don’t do anything about thatch, or you might remove the insects’ home. Make sure you kill off all soil life so the lawn develops complete chemical dependency. You’ll have all the insects you could ever want. –Stuart Franklin, Building a Healthy Lawn, p. 114
Most insects are beneficial, or at the very least, benign. Some naturalists estimate that fewer than two percent of insects fall into the “harmful” category. Many insects, including ladybugs, fireflies, praying mantis, spiders and wasps will actually keep harmful insects from devouring your lawn and will also help to pollinate your plants.
Then, there are the others. Here are a few of those:
Lawn grubs are the larval stage of beetles, all of which go through four stages: egg, larva, pupa, and adult. Most of those that cause damage in North America are scarabs that lay eggs in late June and early July. These hatch a couple of weeks later into larvae, which feed on grass roots until cool weather arrives, molting twice as they grow. They spend the winter four to eight inches underground, well below the frost-line. In spring they surface, feed again, and then burrow back into the earth where they pupate, emerging as adults after several weeks. Some species, such as June bugs, feed throughout the second summer, winter over again, and then pupate and mature the third summer.
Most lawn damage is done in the fall, by the larvae — the grubs.
Identification: Lots of beetles flying about suggests that they are nesting in your lawn, and brown patches that don’t correspond to other problems indicate possible beetle larvae munching. To be sure, dig up a corner of the sod near one of the brown areas and lift it up. If the culprit is grubs, you should catch some of them in the act. A head-count of over ten per square foot constitutes a problem; below that, most experts say there’s no need to take action.
To identify your resident beetles, visit the Ohio State University Extension by clicking on Identification of White Grubs in Turfgrass (PDF). This Fact Sheet encourages you to take a close look at the rear ends of any grubs you may be trying to identify and teaches you what to look for in these close encounters. Should your neighbors catch you at it and accuse you of being a pestophile, we will neither confirm nor deny that you heard it here first.
Control: Let your lawn dry thoroughly between waterings. Virtually all beetles prefer a moist environment, so don’t give it to them. Shallow watering creates ideal circumstances for both beetles and grubs, while deep, infrequent watering can reduce resident grub populations and discourage adults out looking for a good place to lay eggs. If you follow a regular program of watering deeply but rarely, your grass roots will be deep enough to get the water they need even if you let the top few inches of soil dry.
Tip: Control lawn grubs with Scanmask Beneficial Nematodes. Easy to use, just apply as a topdressing to affected areas. Will NOT harm people, pets, plants or earthworms.
When beetles first arrive (usually in late summer or early fall), it’s possible to pick off these pioneers by hand, often preventing a complete infestation. The best time to do this is in early morning, when they’re sluggish.
De-thatch. Thatch shelters grubs, while preventing insecticides or other treatments from reaching them. Removing thatch makes your lawn far less hospitable to these unwelcome guests.
Dance on your lawn. Yes, it’s true. But you have to wear your dancing shoes: a pair of spiked aerator sandals (a.k.a. Spikes of Death) sold as lawn aerators. These sandals probably won’t aerate your lawn (the spikes aren’t big enough, or long enough, and they’re not hollow) but apparently they can do a number on the grub population.
All of the control methods outlined for the Japanese beetle, below, work on most scarabs.
This is the worst problem many lawn-owners face, and perhaps the worst turf pest in North America. Like most grubs, the larvae feed on grass roots, and the adults — those shiny, green-black items as big as a fingernail – feast on foliage, preferring most of all your prize roses.
Since Japanese beetles start as grubs, the methods below should be used in conjunction with the cultural controls described under Grubs just above.
Control: Beneficial nematodes are tiny worms that feed on the larval, or grub, stage of the beetle. It takes a few weeks for nematodes to establish themselves in the soil and to parasitize their grub hosts, so it’s best to apply them before the situation has gotten completely out of hand.
The fine print is important for a second reason: nematodes need to be properly applied, or your time and money will be wasted. They are live beings; they can die. So follow the directions — apply them in the evening, water immediately, and so on — so they can do their work.
Milky spore (Bacillus popilliae). Milky spore is a pathogen that infects and kills not only Japanese beetles but other harmful turf grubs as well. After eating the spore, grubs turn into spore factories, so that when they die, they release millions of the pathogens into the earth. But until the spore concentration is quite high, the kill rate is low. It generally takes two to four years for the spore to build up in soil to the point where it will really cut into a serious grub and Japanese beetle problem. That’s the down side. On the up side, once the spore is established in your lawn, it continues to work for fifteen years or more.
It’s important to use milky spore in the late summer or fall, when grubs are actively feeding in soil that’s still at about 70°F. Warm soil is essential for milky spore development; when soil temperatures fall below 60°F, the stuff won’t spread as quickly. One more warning: if you kill off all the beetle grubs with some other insecticide, the spore won’t multiply and won’t reach the critical concentration for effective control.
For more information, take a look at the very thorough, readable USDA “Homeowner’s Handbook” on Managing the Japanese Beetle (PDF format). It includes photos of all stages of the beetle’s life-cycle, plus info on how to trap them and fight them.
Found throughout the U.S. and southern Canada, chinch bugs are tiny insects (4 mm long as adults, less than 1/8th inch) that feed on lawns throughout their seven-stage life-cycle (egg, 5 nymph stages, adult). They are actually easiest to spot in the two earliest stages, for both the eggs and the first nymph stage are red. Irregular dry or brown patches in the lawn can indicate an infestation. The bugs, which live in thatch, thrive in dry conditions.
By far the most comprehensive discussion of chinch bugs I’ve seen is that designed and maintained by David Patriquin, Professor of Biology at Dalhousie University, in Halifax, Nova Scotia, who devotes several web-pages to this one pest. His page “Facing a Chinch-Bug Problem NOW?” walks the beleaguered lawn-owner through the diagnostic process, then offers a range of control options. Most of these, however, are not legal in his corner of Canada, which has been cracking down on pesticides. Even insecticidal soaps and Neem oil are approved only for some pests, chinch bug not included.
Identification: Look for the red dots that indicate eggs or the first larval stage of the chinch bug. You can also cut both ends off a coffee can (or something of similar size) and push it into the soil in an area where you suspect chinch bugs. When you’ve got the can sunk several inches, fill it with water. chinch bugs, if present, will float to the top.
Control: Patriquin identifies (and details) three levels of control: acute, cultural, and redesign.
For acute (immediate, short-term) control, Canadians are reduced to physical controls such as watering more (chinch bugs prefer dry conditions) and vacuuming the bugs up off their lawns. If you see your neighbor out on the lawn wielding a Shop-Vac on the grass itself, she hasn’t lost her mind; she’s after the chinch bugs.
Patriquin would probably take issue with my tone here; he cites David Slabotsky, foreman for the Parks Department in Wolfville, a town on the Bay of Fundy about a hundred kilometers (62 miles) northwest of Halifax, the capital of Nova Scotia. Slabotsky uses Shop-Vacs on the town’s parks to control chinch bugs and claims that if he catches them early enough, the technique works perfectly.
The full vacuum treatment is threefold:
1.) Rake vigorously around the affected area and towards the middle of it. This destroys the thatch in which chinch bugs live and limits the spread of the pest, should any survive the treatment.
2.) Vacuum both the raked and the infested areas.
3.) Water deeply.
U.S. citizens, while free to wield their vacuum cleaners on their lawns, can also deploy a complex array of tools ranging from diatomaceous earth through insecticidal soap and essential oils such as rosemary.
For cultural control of chinch bugs, Patriquin recommends that one follow all the recognized methods of improving lawn health (mowing high, leaving mown clippings, cutting back on quick-release fertilizers) discussed on this web-site. Removing thatch in the fall is particularly important, since chinch bugs breed and overwinter in the thatch layer. These tactics, which eliminate the environment in which chinch bugs thrive, also “reduce water stress by reducing demand for water,” a critical but delicate balancing act since on the one hand “water stress is the single most significant factor causing lawns to be susceptible to chinch bug damage,” while on the other hand water is an increasingly rare and valuable resource. (Quotes from Patriquin, the page cited above.)
Patriquin’s last level of control, redesign, encompasses everything from overseeding lawns with clover, which makes them more pest-resistant, to replanting especially dry chinch-prone spots with drought-resistant bushes, flowers, and ground-covers.
Sod webworms are the larval stage of a tan or buff-colored moth that is one of the best indicators of an infestation. The moths, which sit out the heat of the day, can often be seen flying in a characteristic zigzag pattern a few feet above the grass at dusk and dawn. The eggs they drop hatch into the worms which do the damage, cutting grass-blades almost at ground-level and devouring them in the silky webbed tunnels that they build in the thatch.
Identification: Jeff and Liz Ball recommend preparing a solution of 2 tablespoons of normal liquid detergent in a gallon of water and pouring this over a pre-marked square of lawn, 2 feet by 2 feet. If your thatch layer is thick, they warn, one gallon may not be enough, because the layer must be saturated with soapy water in order to flush out the webworms. Usually, irritation forces them to the surface within ten minutes.
Control: Like chinch bugs, sod webworms live in thatch, so the best long-term control is to de-thatch and de-thatch thoroughly. However, if your thatch layer is thick enough to be a problem, removing it in mid-summer might stress your grass unduly, as it’s impossible to remove thatch without tearing up a certain amount of grass. You may have to wait.
While you’re waiting for the thatch-control season to roll around, you can spread beneficial nematodes (see above), or you can spray insecticidal soap or Bacillus Thuringiensis (BT), a bacteria which does its dirty work on caterpillars. All of these will kill the worms, but none takes the place of long-term cultural control, which means removing thatch.
Tip: Bt kurstaki (Bacillus thuringiensis) is a naturally occurring soil bacteria that is ideal for controlling webworms in lawns. Very effective, yet will NOT harm people, pets, birds, honeybees, earthworms or beneficial insects.
Moles & Diggers
As mentioned above, most of the small mammals that tunnel so cunningly beneath your lawn are after grubs. Eradicate the grubs, and the mammals will go elsewhere to feed.
Since a mole can devastate your lawn overnight, this means that to stay ahead of them, you must stay ahead of their food source, the grubs. If you’re on top of the grub situation, so to speak, you are unlikely to have a problem with moles or other diggers. If the grubs get the upper hand, though, you might as well hang out a shingle, OPEN FOR LUNCH; MOLES WELCOME.
This section addresses the best organic methods for dealing with specific weeds. For a discussion of more general weeding strategies — how to tackle bad patches of weeds, for instance — and a list of weeding tools, see Weeds, in the page on Long-term Lawn Rehab.
If you’ve glanced at the list of weeds featured here, you’re already aware that it’s far, far from complete. I’ve chosen a few of the most common (dandelions) and obnoxious (kudzu, bindweed) but left out numerous equally deserving candidates (poison ivy and Virginia creeper, to name two). There is almost always an organic alternative to pesticides, though it may take some digging to unearth it and some persistence to put it into practice.
Black Medic (Medicago lupulina)
This yellow-flowered member of the clover family has smaller leaves than the white and purple (strawberry) varieties and grows low to the ground, often in compacted soil where grass does not thrive. It has a single taproot, and unlike the “true” clovers, it does not have stolons (above-ground runners), so it does not form dense mats as those plants do. Like its distant clover relatives, it gets nitrogen from the air and “fixes” it in the soil, thus making it available to other plants.
Control: Black medic can be killed with a number of different organic herbicides, though more than one application may be necessary if the tap-root is unusually long. That same root together with the absence of stolons make it quite easy (and satisfying) to pull when soil is damp. However, killing it is only the first step.
Since this weed thrives in tightly packed soils where grass struggles, loosening the soil is the most important step for long-term control. Otherwise, even if you kill it off this year, it will probably be back. Aerating will relieve the compaction, giving grass a chance to compete. Corn gluten, spread in the fall as a pre-emergent herbicide, can also be a powerful tool, since black medic is almost always a fall-germinating annual.
If the problem occurs at a curbside or path where compaction is a fact of life, grass may not be the best groundcover there. Another plant might well tolerate the soil conditions more easily than grass. Once the new planting is established, it will compete more successfully with black medic than grass did, and it will help control the weed.
Clover, White (Trifolium repens) and Strawberry (Trifolium fragiferum)
Clover was not considered a weed until sometime in the 1950s, when the purification of the Americana lawn reached its zenith, and a lawn-care company developed a weed-and-feed product designed to kill broadleaf weeds such as dandelion and plantain. Since it also killed clover, clover was suddenly declared a weed. Before that, it was valued in part for its flowers and in part because it takes nitrogen from the air and fixes it in soil, thus fertilizing the grass.
Control: In a dense lawn, clover can appear simply as a well-integrated part of the mix. In a sparse lawn, though, it can form a thick mat of above-ground stolons that crowd out other growth. While these densely rooted knots of clover can be difficult to uproot, the stolons also give a garden rake something to catch and pull on. Unless you’re intent on banning clover altogether, it may suffice to break up the mat of interwoven stolons, uprooting some of the plants as you do, and then overseed with grass so as to reduce the density of the patch.
On a warm, windless day, clover patches can also be sprayed with an organic herbicide, which will kill the foliage. The deep tap roots will probably send up new shoots, so check the area for new growth in a couple of weeks.
Creeping Bellflower (Campanula rapunculoides)
Variously known as rampion, rapion, or rover bellflower as well as by the name above, this tuberous weed can gradually take over and dominate almost any space it invades. Introduced from Europe and Asia as an ornamental flower, it has been declared a noxious or invasive weed in several states and provinces, yet it can still be purchased online. The unwary may consider it a desirable addition to their gardens because it will tolerate low light and poor soil, producing in late summer or early fall a deceptively lovely tall spike, fringed on one side with blue or purple flowers.
This insidious weed can safely participate in garden activities only if it is rigorously confined. Trapped between a house wall and a cement sidewalk at least two feet wide, it may be tolerated. If the walkway is narrower, the extraordinary roots, as intrepid as Captain Kirk’s star ship Enterprise and similarly dedicated to going where none have gone before, will travel under the walk and emerge on the far side. If the walkway is made of bricks or flagstones, this weed will insert itself between them.
Bellflower can be difficult to identify, first because its early-season leaves bear a marked resemblance to violet leaves, and second because the leaves on the flower stems bear little resemblance to those first leaves, being far longer and more pointed. Once it flowers it’s easy to spot, but in a lawn where it never gets above three inches tall, it can hide out for years, spreading all the while.
If you suspect creeping bellflower, the only test for a novice is to dig it up. A violet will have a clump of roots; a bellflower will have a thin white or ivory-colored thready root. In a young, individual plant, that will be its only root, but if this little clump of leaves you hold belongs to a colony, then the rootlet will be connected to a taproot shaped like a carrot but colored like a parsnip. Like both, it is edible, as are the leaves.
Control: There’s no easy way to deal with bellflower. The taproots, which can reach the size of large carrots, store so much food that the plant can regenerate even after repeated assaults with conventional chemical herbicides, although it may produce progressively more deformed foliage.
Persistent plucking or spraying: Though killing leaves doesn’t touch or damage the roots, it does stress them, and when repeated often enough, it will kill them. If you’ve got a small patch to contend with and plenty of patience, keep pulling leaves or spraying them with an organic herbicide whenever you see them, and eventually the tap root will be exhausted and die. This may take a couple of seasons, but it will happen.
Digging them up: If you’ve got a large patch in your lawn, the only way to reliably eliminate it is by digging them up, taproot and all. The catch — of course there’s a catch — is that any tiniest fragment of root left behind, whether a sliver of the thread-like roots or a piece of a tap root, will regenerate an entire plant. This is quite a feat, biologically speaking. Since it’s almost impossible to avoid leaving behind at least one or two fragments, digging is usually a multi-season project — but it does get easier (much easier) each season.
Weed cloth: If your patch is located where you can live without grass, the easiest thing to do is smother it by covering it with weed cloth and planting over it. It’s essential that the cloth extend well beyond the borders of the patch, or the leaves will simply emerge at the edge of the cloth and take off from there. It’s best, therefore, to extend the weed cloth a good five feet beyond the fringe of the patch, or to spend an hour or two digging up the worst of the tubers around the edges, to slow it down, Since you’ll be covering the area, you don’t need to worry about leaving shreds of root behind.
Once you’ve prepared the site, lay down weed cloth and either cover it with an attractive mulch such as bark, or pile fresh, weed-free dirt over it, and plant with low, shallow-rooted plants. Trees or shrubs planted on top will send roots right through the cloth, and bellflower will find those gaps and sprout beside the trunks, so smaller perennials work best. For a more complete description of converting a weed patch to a garden click here.
Deprived of light and of leaves, the taproots will die — after one to three years. A thick layer of newspaper (12-15 sheets, with a six-inch overlap between adjacent sets) will speed up this process.
Creeping Charlie (Creeping Charley, Creeping Jenny, Gill-on-the-Ground) (Glechoma hederacea)
A member of the mint family, this small-leaved, ground-hugging perennial spreads and roots through rhizomes, sometimes threading through lawns and competing (successfully) with grass. While it can provide a lovely ground-cover, its tenacious, invasive tendencies have made it almost universally unwelcome, and it is generally treated as an invasive weed. Gardening blogs and advice sites alike attest to the difficulty of eradicating this plant from lawns.
Control: Some recent experiments have shown that using borax can be effective against creeping charlie, but others (U. Washington, U. Iowa) challenge those results. Borax contains the micro-nutrient boron, and as David Lunsford, a Horticulture Technician with the University of Minnesota puts it, “in minute excess amounts, boron has a toxic effect on creeping Charlie.” Unfortunately, in only slightly more minute excess amounts, it is also toxic to grass. In other words, there is only a very fine line between poisoning the weed and taking the lawn out with it. Furthermore, since boron accumulates in soil rather than degrading or leaching away, repeated applications can render soil sterile. No grass, no nothing.
NOTE: At least one other unrelated plant, Lysimachia nummularia, which comes in both green (L.) and golden (Aurea) varieties, is also called Creeping Jenny.
Dandelions (Taraxacum officinale)
There are actually a number of dandelion species and dandelion look-alikes, so many that a search for “dandelion” at the USDA Plant Database calls up a list of over 60 items. At least two look-alikes can find their way into North American lawns (also gardens, roadsides, window-boxes, you name it). First there’s a fall-flowering version (Leontodon autumnalis) known, not surprisingly, as fall dandelion (or hawkbit), and then there’s Hypochoeris radicata, false dandelion, a.k.a. catsear or cat’s ear.
The plant most of us are talking about when we say “dandelion” is the Taraxacum officinale whose name, interestingly, means “official remedy of disorders.” All parts of the dandelion (leaves, flowers, root) are edible, and numerous dandelion recipes are available in books and online. If you eat it, however, start with small amounts, as some people do have allergic reactions to large doses. (Leaves and roots of the two look-a-likes mentioned above are also edible, but other similar plants are not. Be sure you know what you’re dealing with!) Dandelion leaves contain vitamins A and C, beta carotene, calcium and iron; the flowers supply vitamin A and fiber, and the roots can be boiled, fried, or dried and then ground into a coffee substitute. Medicinal uses of roots and leaves abound.
Although dandelions do absorb more than their fair share of nutrients in a lawn, their deep taproots help aerate clay soils, and their flowers attract and feed ladybugs, one of the most beneficial insects for a garden. So if you don’t manage to dig all of them out, at least you can know that they are doing some good. Composting the ones you do dig out will return all those nutrients to your soil. To ensure that the flowers don’t mature or that mature ones can’t germinate, dig them into the center of the pile, or just be sure they’re well-covered and wet.
Despite their many uses, for many North American gardeners the dandelion is public enemy #1 (or at least in the top ten) and most owners want recipes not for eating, but for eradicating.
Control: You can make your lawn less appealing to dandelions in a couple of ways. They love alkaline soil, while grass prefers a slightly acidic soil, so you can discourage them by lowering the pH. (Add sulfur. See Soil Amendments in Long Term Lawn Rehab.) Since tall, dense grass tends to crowd them out and deprive them of the sun they crave, mow high. A closely shorn lawn allows a dandelion’s circle of leaves to spread wide over the grass around it, collecting all the sun it needs and wants; long, dense grass forces those leaves upwards, starving them of light and ensuring that they’ll get chopped short when you mow.
Don’t let dandelions go to seed. Mow before the flowers mature to prevent new plants from springing up. Pollinated flowers may still go to seed even after they’re cut from the plant, so the earlier you get them, the better.
The old standby, digging, sometimes appears to have no effect at all because, yes, a dandelion will indeed re-sprout if any of the root remains in the soil. That big tap root stores enough energy to send up several rounds of new vegetation. However, if you consistently yank the leaves, you will keep the plant from performing the photosynthesis which replenishes the root. Keep pulling the leaves — and even better, the leaves plus as much of the root as you can — and you will exhaust the taproot. The dandelion will die.
Vinegar alone or any organic herbicide will shrivel the foliage of a dandelion within hours on a warm day. These are not systemic herbicides (they don’t get carried through the plant’s system into the roots), so the root will indeed sprout new leaves. However, repeated applications will eventually exhaust the root’s reserves, killing the plant.
Tip: Made from clove oil and citric acid, BurnOut Weed & Grass Killer is a broad spectrum natural herbicide. Kills weeds in eight hours or less. Degrades rapidly and will not move through the soil to injure nearby plants.
Field Bindweed (Convolvulus arvensis)
Known throughout the west as one of the worst weeds a farmer can face, bindweed usually sticks to fields. If it does turn up in a lawn, it presents the hapless homeowner with many of the same problems as does Creeping Bellflower. Like bellflower, bindweed has a deep, extensive root system that can regenerate from even a tiny fragment. Bindweed does not have tap roots, but it makes up for this by extending so deep into the soil — up to twenty feet — that the sidewalk that can confine bellflower is useless against bindweed.
A member of the morning-glory family, field bindweed has the pretty, bell-shaped flowers typical of that family, always in white, pale pink, or a combination. The flowers are small but showy, the leaves heart-shaped. As its name implies, it is a vine that can and will climb anything, yet it adapts easily to lawn-life, simply spreading out horizontally rather than vertically. Again like bellflower, bindweed is tenacious, and any assault against it must be considered a multi-year project.
Control: Dig out young plants: Really young plants are easy to pull and will not grow back, so if you live in an area where bindweed occurs in gardens, it’s worthwhile to learn what the seedlings look like.
Flower plucking: Though bindweed propagates primarily through root-spread, it does occasionally sprout from seeds, as the seedlings testify. Plucking the flowers will prevent seeds from forming, but it needs to be done each day, as flowers only last for 24 hours.
Shade it out: since bindweed prefers sun, shade will stress it. Farmers have reported some success in controlling bindweed in corn fields, simply through shade.
Cultivation: A number of sites recommend cultivation (hoeing or some equivalent). Like any other method that continually stresses the plant and denies it the chance to perform photosynthesis, this will eventually kill the plant — but like all the other such methods, it must be kept up relentlessly for several years. Otherwise, all it accomplishes is to break up the roots, creating new plants.
Mulching: Some authorities report that covering a patch with black plastic for several hot weeks in summer will kill it, but these reports are inconclusive. Everyone agrees, however, that if it is deprived of light for several seasons, it will die. The problem is that you cannot use the earth while it’s covered with black plastic.
Nutsedge, Purple (Cyperus rotundus) and Yellow (C. esculentus)
Purple nutsedge has been declared one of the worst weeds in the world, having invaded over fifty crops in some ninety countries worldwide. Though purple and yellow nutsedge are distinct species, they cause similar problems in a lawn and respond to similar organic controls.
The nutsedges are indeed sedges, not grasses, so they tend to grow in damp, heavy soils, though they show a marked preference for sunny locations over shady ones. Their leaves, triangular in cross-section, grow from the base of the plant in groups of three, and their curiously spare flowers, yellow or purple-brown depending on the species, almost resemble seed-heads more than flowers. What seals the identification of a nutsedge is the existence of tubers measuring up to half an inch in diameter on the rhizomes. New plants start exclusively from these tubers (misnamed “nuts”), which grow only at the ends of rhizomes for yellow nutsedge, but along the rhizomes for purple nutsedge. After winter dormancy, the tubers start producing new foliage at about 43° Fahrenheit for yellow nutsedge, but not until almost 60°F for purple.
Control: Hand-weeding: As with all especially persistent weeds, early identification and action make control far easier and more likely to succeed. And as is true of even the most pernicious weed, consistent defoliation through the growing season will eventually exhaust the reserves of the most extensive root system. Weeding regularly, every two to three weeks, will indeed kill even purple nutsedge.
Digging: For small patches in lawns, U.C. Davis recommends digging up the plant, being careful to go eight to twelve inches down so as to extract the entire root system. The sod can then be replaced — if it is free of rhizomes and root buds! — or the patch can be reseeded (see Pests in Gardens and Landscapes).
Mulching: Any plant can be killed eventually by depriving it of light, but the plastic mulches that work on most plants don’t work on these sedges: their sharply pointed leaves can pierce most such materials. (Whether they could also pierce ten to twenty sheets of newspaper beneath these mulches isn’t clear.) Tough polypropylene weed cloth can suppress nutsedges if left in place for long enough, though it’s always necessary to check for new growth and yank it after removing the mulch.
Kudzu (Pueraria lobata)
Kudzu is the stuff of nightmares and really bad science fiction movies, but it’s real. This legumous vine, the scourge of the southeastern United States, can grow at several feet per week, enveloping entire trees, which it kills by depriving them of light and water. It is most spectacular when draped over a thirty-foot-tall tree, but left unchecked, it will take over whatever is in its way, including your lawn. Various methods of control are recommended, including goats, but as Chad Hower, author of the website Kudzu World puts it, “a large number of goats is required as kudzu will grow on goats if they stand still too long.”
The history of kudzu is rife with irony. Now reported as invasive by states as far west as Missouri, Texas, and even Oregon, kudzu was originally imported (imported! on purpose!) to decorate the Japanese pavilion at the 1876 Centennial Exposition in Philadelphia. Americans adopted it as an ornamental, finding its flowers lovely and its dense foliage ideal for shading porches. In a move that today makes one want to weep, various government agencies promoted it in the nineteen twenties and thirties for use as erosion control and fodder. Farmers were paid (paid!) to plant millions of the vines in these decades — between 73 and 85 million, depending on the source.
In Japan and China, where kudzu is native, the roots are used for medicinal purposes as well as to make a variety of starchy and tofu-like foods, the vines are processed into baskets and clothing, and the leaves and flowers add color and fiber to various recipes. Americans are now following suit, making baskets from stems, jam from flowers, and various other edible concoctions from the leaves. Fodder, paper, sculptures, and quiche are a few of the more creative uses to which kudzu is now put.
Unlike rhizomous plants like bindweed, kudzu does not send out horizontal rootlets below ground, but above ground, like strawberries. Every twelve inches or so, these stolons develop thickened spots, or nodes, from which roots start growing downwards and vines start growing upwards. Eventually, these nodes harden and widen into what are called “crowns,” below which extend taproots that out-weigh any others you’re likely to encounter.
Control: The Coalition To Control Kudzu Without Chemicals, a grass-roots group based in Spartanburg, South Carolina, maintains a web-site that offers a great deal of information about kudzu itself and about chemical-free coping methods. Their page “Managing Your Kudzu — no longer active” gives advice about controlling both the vines on your own property and the stuff trying to invade over a property line. The group has a field-testing site where it conducts ongoing experiments with a variety of techniques, including those described here — and others, including the use of a skid-steer loader (“Bobcat”), which they document on its own page, along with one of my favorite lines:
He’s in there somewhere . . .
Remove Crowns: It’s hard to imagine any good news connected with such a voracious plant, but there is some: you don’t have to dig out the taproots! This is fortunate, as these taproots can be man-sized or bigger; some of the oldest in Japan are estimated to weigh hundreds of pounds.
What kills kudzu is the removal of the root crowns. Merely cutting the vine so that it’s no longer connected to a crown will not kill the plant, except when the crown is actually a very young node. Once the node has become a crown, it has also grown its own taproot, where it stores plenty of food. The crown, or any piece of it left in the ground, can draw on that store and generate new vines. Root crowns — or again, pieces of them — can indirectly regenerate whole plants if separated from the root, as long as they haven’t dried out. They’ll simply send out a new shoot, which forms a node, which roots, and voila: a new kudzu plant.
Just locating crowns under the mass of foliage can be difficult, and the crowns themselves can be quite tough and big. Some grow as large as soccer balls. Cutting them out is therefore not easy, but a sturdy pruning saw is a good place to start. The Coalition has a page on “Surgical Crown Removal” which features photographs and descriptions of useful (and useless) tools and techniques. Since the stolons grow above-ground, it’s often possible to follow them from crown to crown.
Cut vines from root crowns: If kudzu is encroaching on your lawn, you can keep it from getting a foothold by cutting the new vines from woody root crowns. DO NOT MERELY PRUNE the vines, cutting them partway back; this is a self-defeating move! In other words, if at all possible, do not cut a vine anywhere save at its point of origin at a root-crown. Severed vines not only grow back, but they multiply, Medusa-like, because the undamaged tip of a vine contains a hormone called auxin which prevents such multiplication, and if you cut off only part of the vine, you remove this inhibiting hormone. The pruned vine responds by putting out new shoots at every possible place, which means from the “buds” at the base of each leaf. Where you once had one vine now you’ve got five, and if you persist, there’s no telling where it will end.
A weed eater or string trimmer is an effective tool for cutting young vines from crowns, and repeated, aggressive attack can even damage the crown itself.
Defoliate: Repeatedly stripping a vine of its foliage will also, as always, kill a plant — eventually. In the case of kudzu, this is only practical with young, low plants. It’s pretty hard to strip the foliage from a one-hundred foot-long vine that’s gone up one side of a tree, down the other, and then across a meadow, which is why removing the root-crown entirely or at the very least cutting the vine from the crown is not only more effective, it’s often easier.
If, however, you can’t get at the root-crown (it’s on your neighbor’s land, it’s under a big rock, whatever) then cutting the foliage from older, woody vines is the next-best thing. (“Woody” here is metaphorical; like most vines, kudzu doesn’t bother producing a trunk, which is why it has to climb other things: it’s not strong enough to support its own weight.) As always with persistent perennials, this stripping will have to be repeated numerous times to be effective.
Mow like crazy: Young kudzu that has actually gotten established in a lawn can be checked, if not killed, by repeated mowing. This won’t damage the root crown, since a mower passes right over crowns, but repeated defoliation will eventually kill a young plant. Mowing of course does precisely what you were warned not to do above: it cuts the vines back, rather than cutting them off at the source. However, since mowing happens repeatedly and regularly, the new growth never gets fully underway.
Compost the leaves: I know, this isn’t a method of control, but really — what are you supposed to do with all that stuff after an afternoon fighting kudzu? Compost it. This is the one tip that doesn’t come from the fine folks at the Coalition, though as it turns out, many of them do it. Charles H. Wilbur, whose tomato plant made it into the Guinness World Record Book of 1987 and who regularly grows massive vegetables, does it all organically. His secret? Kudzu compost. Kudzu wasn’t the only ingredient in his compost, but it was certainly a major component. Read all about it in his book, How to Grow World Record Tomatoes. Newt Hardie, one of the original founders of the Coalition, informs me that it’s perfectly safe to compost the root crowns as well, as long as they dry out first. (E-mail exchange with the author, June, 2008.)
(My thanks to Newt Hardie for his many suggestions on this section.)
Spotted Knapweed (Centaurea maculosa)
Spotted knapweed, diffuse knapweed, lesser knapweed, squarrose knapweed, black, brown, meadow, and Russian knapweed — all of these, in addition to yellow starthistle (Centaurea solstitialis), cause greater or lesser problems depending on location and luck.
In lawns, correctly identifying the type of knapweed is not critical, as organic controls will be the same. However, if you’re not sure what you’re looking at and you’d really like to know, see Biology and Biological Control of Knapweed.
Like starthistle, knapweeds belong to the genus Centaurea, and all begin as rosettes — a ring of leaves originating from a common center, like a dandelion. They put down long taproots and can grow to be several feet tall, with bushy flowers — pink, white, purple, or yellow, depending on species — that resemble those of a thistle, to which they’re related.
Of them all, probably spotted knapweed is the most wide-spread and most troublesome. It’s at the top of the invasive weed list in many states and provinces, and concerted efforts are underway to slow its march across grassland. Why? Because it gains ground by poisoning surrounding plants with niacin. Most knapweed plants will be surrounded by a little circle of bare dirt, because they’ve poisoned all the nearby plants. It is a therefore a scourge of rangeland, since it kills grass but cattle and other foragers won’t touch it.
Control: Control in a small plot is a very different proposition, and a much more manageable one, than control across open fields and prairies. Mow frequently and water — water washes away niacin — to keep knapweed from poisoning other plants. Most frequently, though, it’s necessary to pull knapweed up by the roots. This is, obviously, much easier when the plant is small, so if you’re in a knapweed district, keep your eyes open and act fast.
Though a few turf diseases can be caused by viruses or bacteria, virtually all are caused by fungi. The spores, always present in the soil, take advantage of any weakness to get a foothold in the turf. Therefore the best defense, as always, is a healthy lawn, and the second-best is early identification and response.
Identification can be difficult, since so many lawn diseases result in pretty much the same symptom, irregular patches of brown grass. In early stages the diseases can be more clearly differentiated, so the sooner you notice a problem, the better. To pin down the culprit, it’s a good idea to check out the pictures at a number of different sites, rather than relying on just one.
There are many more diseases than the few described below. The section in the Appendix on Dealing with Pests and Problems suggests several sites that go into more detail than I do here.
Dollar Spot (Sclerotinia homeocarpa)
Symptoms: True to its name, dollar spot looks at first like small, round disks of grass gone bad. These spots grow, however, and may soon overlap, meaning that this disease will begin to resemble a dozen others characterized by patches of dead or dying grass. Dollar spot on turfgrass can still be distinguished from these in part through the patches of mycelium that are visible on the grass in early morning. Mycelium, which in this case looks almost like small, thick spider webs or like cotton balls pulled very thin, is actually fungal growth itself. Dollar spot also will usually cause tan lesions (bruises) with red borders at the tips of the leaves.
The disease tends to appear in summer, when the grass has used up its spring supply of nitrogen and the weather is dry. Temperatures between 60 and 80 degrees are perfect for it, since it prefers warm days and cool nights.
Control: Once diagnosed, this disease can be controlled with low to light dosages of nitrogen, and regular mowing. Liquid seaweed extracts (quick-release fertilizers) appear to be especially effective in restoring affected lawns when they’re first diagnosed. However, as soon as the problem is under control, switch to a slow-release fertilizer such as blood meal or organic cotton-seed meal so that the grass receives a continuous supply of nitrogen throughout the season. This will help prevent re-occurrences.
Deep watering also helps, but it’s important not to leave the grass damp overnight, as this encourages the fungus.
Lawn rust is an equal-opportunity disease, afflicting any grass type anywhere in North America. It does have a preferred time of year, however, tending to strike in hot, dry periods in spring or fall.
Symptoms: Look for yellow to red patches on grass stems. These patches are not dry lesions, but accumulated mold spores that you can easily rub off.
Control: Mow frequently, and don’t leave the clippings! Water in the early morning hours to give lawns time to dry out during the heat of the day. Organic fungicides containing copper or sulfur can be used to prevent rust spores from germinating.
Symptoms: Fairy rings are well known as a circular growth of mushrooms that springs up after heavy rain, and the mushrooms are indeed a cause and not merely an effect of the problem. The rings appear early in the season as irregular circles of deep-green grass, the color resulting from a release of nitrogen as the mushroom mycelium breaks down organic matter in the soil. Eventually, though, this rather pretty phenomenon gives way to one less charming, as that lush green turns gradually to brown on either the inside or outside of the circle.
Control: One of the easiest of diseases to identify, fairy rings are one of the hardest to eradicate. If your back is strong, you can dig out the infected earth, but this can be a major undertaking, as you need to go two feet down and at least one foot beyond the ring on either side of it. Accounts differ as to what you should to do with the earth. One source says to mix in compost and return it to the trench; another says to dig it out and, presumably, dispose of it.
Experts also disagree about the effect of deep watering, for while one says to avoid it, another says to do it. Neither seems quite sure of the advice he or she is offering.
One thing they do agree on is that the rings are very difficult to remove permanently. Kicking over mushrooms appears to be as good a method of control as any.
Brown Patch (Rhizoctonia solani Kuhn)
Warren Schultz calls this Public Enemy #1, as it’s the most common lawn disease in the continental U.S., sparing only Washington and Oregon, and appears through most of Canada as well. Like rust, it can strike any grass, anywhere. It thrives in humid weather at temperatures between 80 and 85 degrees, so brown patch usually strikes cool-weather grasses in summer and warm-weather grasses in spring or fall. Lawns fed on synthetic fertilizers and regularly dosed with pesticides are particularly vulnerable.
Symptoms: The disease shows up as circular or roughly circular patches a foot to several feet in diameter that first appear dark, as if bruised or soaked with water, and then turn brown as the grass dies. These patches will eventually spread and overlap, leaving irregular brown areas.
Control: The disease is encouraged by wet conditions and poor drainage, so treatment is all about improving drainage. Many fungicides may paradoxically worsen the situation by killing off earthworms and other soil organisms that aerate the soil and make it more porous. Drainage can be improved by topdressing, especially with rich organic matter, and by aerating in spring and fall. Grass afflicted with brown patch should not be fertilized, as nitrogen encourages the disease.
Note that though brown patch and dollar spot appear almost identical once they are established, their causes and their treatments are precise opposite. Here’s an object lesson in the importance of accurate diagnosis: get one of these wrong, and your treatment is likely to hurt rather than help the situation.
Dogs and Lawns
Pets, in particular our furry canine friends, aren’t always kind to our lawns. Let’s not even get into digging; let’s stick to damage caused by activities that aren’t going to go away: bathrooming. If you have a dog, you already know that its urine and feces can create dead, brown patches on your lawn. This is because they are so high in nitrogen that they can cause precisely the sort of burn spots that overdoses of nitrogen fertilizer cause. (Urea is in fact a primary ingredient in many synthetic fertilizers.) You’ve probably noticed that the disc of dead grass is often surrounded by a bright green ring. The grass around the urine spot, where the nitrogen thins out, will be feasting off the diluted nitrogen, while the grass underneath has been killed by the overdose.
Urine usually causes worse problems than feces because, being liquid, it zaps the grass almost instantly, while feces have to dissolve before taking full effect. Also, it’s a lot easier to remove a pile of poop than a spot of urine, so feces often don’t stay on the grass long enough to hurt it. Then, believe it or not, gender plays a role, and here we get into the details of gender-determined peeing style. Females do the most damage, because when they stoop to pee, their urine falls in a concentrated spot. The leg-lift characteristic of males, on the other hand, sprays the urine over a wider area — one that is often not in the center of the lawn. Also, since males “mark” territory, often they leave only a bit of urine in any one place.
Though some things will mitigate the damage from a bad burn (see the list below), nothing can cure it. On at least one page, no less reputable a source than Cornell University actually ducks the problem, recommending that dog-owners trade in their dogs for cats. So the two terms in this heading (“dogs” and “perfect lawn” can’t really co-exist except in writing. Out in reality, you’re going to have to make some choices and some compromises — or find a dog that won’t pee on your grass.
Aha. If you can’t cure the problem, perhaps you can prevent it from occurring. In other words, the only way to mix a perfect yard with a dog is if the dog, too, is perfect — or nearly so. In practice, this means that you need to train the dog not to urinate on the lawn. Set up an area in a corner covered with bark or gravel, and train the dog to urinate only there. This is perfectly doable, given the time and the dedication on your part, and if you’re up to it, it’s not only the best solution, it’s the only one.
Dr. Steve Thompson, Director of the Pet Wellness Clinic at Purdue University’s extensive School of Veterinary Medicine, outlines how to do this in a brief but useful article, ‘Dog-On-It’ Lawn Problems, Updated, which you can find on Texas A&M University’s website.
In the meantime, here are some things you can do to mitigate the problem:
• First, determine your tolerance levels. A few odd burn spots here or there may not matter to you, but may to someone else. Or maybe what was under control now isn’t (your dog just had puppies, for instance) and suddenly, your limits have been breached.
• Remove feces promptly. Pour water on areas where the dog(s) has urinated, to dilute the uric acid that causes the problem. This does help — but it assumes that you will be on hand to see when and where your dog pees, and that you’ll be scrambling after her, watering can at the ready.
• Try sprinkling urine spots with sawdust, then dampen the spot. The decomposition of organic matter requires nitrogen. Since sawdust doesn’t contain much, it will take it from the soil — which, in this case, has plenty of extra nitrogen.
• Other sources — several of them — recommend that you patch the burned areas. Remove and compost the dead grass, and replace it with discs of new sod. This would certainly do the job, but it’s a lot of work, it takes time for the new grass to root, and who has extra sod lying around? Worst, it doesn’t address the ongoing problem. So this idea is practical, really, only if you’ve inherited a lawn with urine spots, but not if you have a dog that’s still got the run of the yard.
• Build a dog run, or give the dog free rein in the back yard, but not in the front. This way, you can keep part of your yard pristine. The down side (for some) is that now your dog is confined; you aren’t sharing the space, but living in parallel yards.