Natural weed control

At this point, the weeds seem innocuous enough — just so much green confetti scattered among the flowers and the veggies. Yet by late spring/early summer, their vigor and swelling numbers can be enough to make the couch and TV more appealing than the garden.

This column is about how to prevent or eradicate weeds. But first, let us honor the multitude of gifts these plants’ riotous diversity bestows on us.

Weeds are the original cover crop; they are there when we’re too distracted or demoralized to plant one ourselves. The leaves and roots of weeds shelter, hold and feed the soil. Their vigorous root systems dig deep, often penetrating and fracturing hardpan (and thereby easing the way for future crops). Weeds pull minerals from these depths (and, by their death and decay, make those minerals available to our crops). They shelter both beneficial insects and many weed-specific (admittedly not always specific enough!) pests, which then provide food and nurseries to the aforementioned beneficials.

I rely on weeds such as lamb’s quarters, purslane and sheep’s sorrel both for food and for early, exotic greens to take to market. Plantain draws the poison or irritant from insect stings and bites (chew it up and apply the macerated weed to the bite or sting, renew often till the pain/itch subsides). In the field, I use yarrow to stanch the flow of blood from bad cuts. I use burdock to ease the symptoms of bruises. Evening primrose and giant ragweed stalks bulk up my summer compost pile, enabling it to breathe and avoid going anaerobic. Finally, such “weeds” as black-eyed Susan, Queen Anne’s lace, goldenrod and joe-pye weed are mainstays in our summer bouquets.

This is but a sampling of the virtues of weeds; many sources more qualified than I am have expounded on the subject at length. Two of my favorites are the now out-of-print book Weeds: Guardians of the Soil and the writings of my naturalist friend “Ranger Doug” Elliot (or, better yet, a weed/wild-food walk with Doug).

As for prevention, the first key point, of course, is don’t let weeds go to seed. Every spiny amaranth or Galensoga (to name but two) that sets seed in your garden opens the door to the arrival of thousands more. These seeds can remain dormant for years and then sprout when disturbed. And don’t mulch with hay unless you’re willing to keep on mulching. Most hay is loaded with weed seeds.

Note: There is a school of gardening (championed by the late Ruth Stout) that advocates the constant, heavy application of spoiled hay. In her day, Stout apparently had ready access to abundant, free spoiled hay. Nowadays, however, the stuff that’s available usually sells for a buck a bale. If your garden is small enough or your budget large enough, this system may make more sense for you than it does for me.

Weed-free mulches such as grass clippings (from lawns that haven’t gone to seed), leaves and straw are one of the best solutions to weed problems. If you have the resources (and the presence of mind) to mulch as you transplant, by all means do it. If you don’t have the mulch or the time to apply it, you can apply corn gluten to the soil you’re transplanting into. Corn gluten acts as both a source of nitrogen and as a pre-emergent herbicide. Obviously, this won’t work with direct-seeded crops. Warning to growers who want to be certified organic: There may be problems because of the likely presence of GMOs in the corn gluten.

Mulching is a less satisfactory solution for direct-seeding. Sure, you can mulch both sides of a newly planted seed row, but that doesn’t mean there won’t be a zillion weeds popping up in the row itself, along with (and often well before) the seeds you’ve planted.

Stale-bedding solves this problem most effectively. You let a garden bed go stale the same way you let a loaf of bread go stale: by making the bed and then just letting it sit there.

Actually, that’s not quite accurate: A stale bed does need to be kept watered, because the point is to flush the weed seeds.

The idea is to get all of the soil disturbance needed for amending, shaping and preparing a seed bed out of the way before you let it go stale. Then, when you have a good crop of newly emerged weed seedlings, you kill them with the least amount of soil disturbance possible. You can do this by using one of the many styles of cultivating hoes, such as the stirrup hoe, the Winged Weeder, or that gardener’s version of farming’s rotary hoe, the Garden Weasel.

The reason for minimizing soil disturbance is that you’re looking to exhaust the weed-seed deposits in the top inch or so of soil. Every time you work the soil, you’re delving into your weed-seed bank, bringing new seeds to the surface. The more soil you work, the more weed seeds you bring up. If you stay very shallow in your cultivating, as few as two or three flushes of weeds may be enough to exhaust the weed-seed deposits in the top inch or so of soil. This approach makes it possible to grow even slow-germinating crops such as carrots, parsnips and many flowers and herbs with only one modest weeding session before they reach a size that makes mulching practical.

I choose to flame my stale bed; that way, I’m not disturbing the soil at all (and therefore, I am bringing no new weed seeds to the surface). I can also plant a bit of seed the day before I seed the entire bed. When this bit of seed germinates, I know I can flame the bed one last time, just before my crop emerges. By doing this final flaming, I ensure that any weeds will be on the same footing as my crop, rather than way ahead of it.

Once the crop is up, I switch to cultivating tools. My favorites are the Winged Weeder and the Garden Weasel. Like many cultivating tools, they work on the principle of getting the weeds when they’re small (ideally, in their infancy).

As farmer Kenny Haines says, you “want to catch them in that white-hair stage” — that is, just as they’re sprouting that first white root or radical. At this stage, they’re utterly vulnerable. Disturbance exposes the newly emerged radical to drying out, and they die.

Kenny recommends getting out there as soon after a rain or irrigation event as the soil allows and cultivating that top half-inch or inch. When I do that, I find that the work goes very quickly and easily, and my plantings remain virtually weed-free.

Sound too good to be true? Well, the Garden Weasel, for instance, can be used in as little time as it takes to roll it between or even over your newly emerged rows (all three of the Weasel’s spiked wheels are removable, making it easy, for example, to remove the middle one to straddle rows). Note: The Weasel is totally ineffective against larger, well-rooted weeds and perennials. And those ads (and gardeners’ fantasies) that make it out to be some kind of mini-tiller are laughable — at least until you break it trying to use it that way.

Cultivating is most effective if your seed rows are laid out so they just accommodate the tools you plan to use. And if your soil’s fertility will allow it and fungal diseases are not a problem, you ideally want to plant so that, at maturity, your crop will completely shade out the spaces between your plants.

Of course, unless you mulch with the likes of cardboard, black plastic or landscape fabric, none of the previously described tactics will eradicate such pernicious weeds such as Johnson, quack and Bermuda grass, mugwort, nut sedge, etc.

Apart from such heavy-duty mulches, the only other organic options (short of removing every piece of root by hand) are to bare-fallow or smother-crop the infected area. Bare-fallowing is most effective in hot (or deeply cold) dry weather. To accomplish it, till or plow up the infected area. Cultivate this patch every time you see green or at least every week to 10 days. Depending on the weather, this process can take from three to six weeks or more, and it’s hard on the soil. If the weather is cooperative, however, it’s the most effective method.

Smother crops are very vigorous cover crops, such as Sudan grass, buckwheat, cowpeas, rye or hairy vetch. They eradicate weeds by forcing them to exhaust their reserves trying unsuccessfully to compete with the smother crop.

This final tip may get me in trouble with gardeners’ significant others. 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 might get simply by being tilled out and back into the soil. I have yet to try this one. But if you’re single or have an equally obsessed spouse and excellent night vision, let me know how it works.