At ot first weeds, innocuous — enough just green confetti scattered among flowers and vegetables. In fact, weeds bestow a multitude of gifts on us, from holding and protecting bare soils and providing habitat for beneficial insects, to their use as edible and medicinal plants (see “Get to Know Your Weeds,”). Weeds compete with garden crops for space, water and nutrients, however, and if not kept in check, they can seriously affect crop yield and quality.
The key to preventing weeds from becoming a problem is to remove them before they produce seeds. Every pigweed or galinsoga plant that sets seed in your garden opens the door for the arrival of thousands of its offspring. These seeds can remain dormant for years and then sprout when you hoe or till, which brings them to the surface.
Although some gardeners use chemical herbicides to kill weeds, research suggests these pose health risks for humans and are damaging to the environment. Furthermore, they’re simply not the most effective way to control garden weeds. Herbicides, after all, are designed to kill plants. Fortunately, though, you can manage weeds with easy and safe organic techniques. Basic Weed Prevention Mulch. Using weed-free mulches is one of the best methods of preventing weed problems.
Good options include mulching with leaves, straw or grass clippings. Fresh grass clippings from lawns that haven’t been treated with herbicides are a great choice because you can get them free from your lawn and from neighbors’ lawns.
Grass clippings contain about 4 percent nitrogen and provide a slow — release fertilizer as they decompose.
Straw is the material leftover after grain has been harvested, and it makes a good mulch because it contains few weed seeds. Hay (dried grasses) can work well, too, but talk to a reputable supplier and make clear you intend to use it as mulch to be sure it isn’t full of grass seeds.
A method of gardening championed by the late Ruth Stout advocates the heavy application of spoiled hay, but if your hay is full of seeds, this method only works if you keep piling on more and more.
Mulching works well for transplants, but it’s not a great option when you’re direct seeding. That’s because you can mulch both sides of a newly planted seed row, but that will not prevent weeds from popping up in the row itself — often appearing even before the seeds you’ve planted.
Corn Gluten. If you don’t have mulch or the time to apply it, consider corn gluten. This nontoxic, plant- based herbicide is a byproduct of corn processing that kills germinating seeds and also provides a source of nitrogen. You can’t use corn gluten with direct- seeded crops because it may kill the seeds, but it’s a good option for transplants. You can buy corn gluten products from garden supply companies. Organic growers should be aware that corn gluten may be made from genetically modified corn.
Stale Seed Beds. “Stale bedding” is a good option for direct-seeded crops. The idea is to reduce weed problems by exhausting the weed seeds in the top inch or so of soil without bringing new seeds to the surface. Till the bed then water it, and when a good crop of weed seedlings emerges, kill them with the least soil disturbance as possible, such as with a flame weeder or scuffle hoe. If there’s time, repeat the process. This approach makes growing even slow-germinating crops — including many flowers and herbs — possible with one modest weeding session before they reach a size that makes mulching practical.
Flame Weeding. I like to flame my stale beds so I don’t disturb the soil at all, and I don’t bring new weed seeds to the surface. I also plant a bit of my crop seed a couple of days before I seed the entire bed. When the first seed germinates, I know I can flame the bed one last time — just before mymain crop emerges. This final flaming ensures that any weeds will begin on the same footing as my crop, rather than way ahead of it.
Cultivating Tools. As soon as the crop is up, I switch to cultivating tools. My favorites are the lightweight Winged Weeder (see photo, http://seeds.rucenter.biz) and the Garden Weasel, which has wheels with prongs that make turning up the soil easy. Like many cultivating hoes, these tools w ork on the principle of getting the weeds when they’re small — ideally in the weeds’ infancy.
According to North Caro lin a farm er Kenny Haines, you “want to catch them in that white h a ir stage” — thatis, just as weeds are sprouting that first white root. A t th is stage, they’re utterly vulnerable. Disturbance exposes the newly emerged roots to drying out, and the roots die. Hain es recom mends cultivating the top halfinch or inch of soil as soon as possible after rain or irrigation. If I do that, I find the work is quick and easy and my plantings remain virtually weed-free.
Cultivating is most effective if your seed rows are spaced just widely enough to accommodate the tools you plan to use. If your soil’s fertility will allow it and fungal diseases are not a problem, you can also prevent weed growth by spacing plantings so that, at maturity, your crop will completely shade the spaces between rows. Eliminating Noxious Weeds Unless you mulch with cardboard, black plastic or landscape fabric, none of the previously described tactics will eradicate such pernicious weeds asm ugwort, nutsedge, or Johnson, Bermuda and quack grasses. Apart from such heavy-duty mulches, the only organic options for eradic a tingthese weeds — short of removing every piece of root by hand — are to bare-fallow or smother-crop the infected area.
Bare fallo wingis most effective in hot (or very cold), dry weather. First, till or plow the infected area. Repeat every time you see green, or every seven to 10 days. Depending on the weather, this process can take three to six weeks or longer, and it’s hard on the soil. If the weather is cooperative, however, this is the most effective method.
Smothercrops are vigorous cover crops, including buck w h eat, cow peas, hairy vetch, rye and Sudan grass. They force weeds to exhaust their reserves while trying unsuccessfully to compete with the smother crop. Just be sure to cut down your smother crop before it produces seeds of its own.
Some researchers and farmers are experimenting with working the soil in the dark. Apparently, many seeds need just a brief exposure to light to break their dormancy, which they can get simply by being tilled up and turned back into the soil during daylight hours. Working the soil in the dark is supposed to eliminate this problem. I have not tried this method , but if you’re single or have an equally obsessed spouse and excellent night vision, let me know how it works.