Using chemical weed killers may seem like “science.” But for consumers, it’s a crapshoot.
You never really know how effective an herbicide will be, since it depends on weather, timing, how well you follow the directions and other factors. Even worse, you never know what it’s going to kill besides your targeted weeds.
Herbicides almost always kill or harm something else, such as desirable plants, microbes in the soil, or marine life when the chemicals wash down storm drains into lakes and streams. This includes “weed and feed” products (combined herbicide and fertilizer) and weed killers marketed as “selective” or “pre-emergent.”
So this weed season, save yourself money and uncertainty. Avoid high-powered chemical weed killers. Ignore the militaristic “wipe out weeds” advertising, and the huge displays of herbicides in home improvement stores.
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In most cases you don’t need to nuke ‘em, even though this is a banner year for weeds locally, thanks to our mild winter, relatively sunny spring and a few good rains. The weeds are growing like, well, weeds. But you have other options.
Three sheets to the weeds
Get ahead of the game by making sure weeds don’t have many attractive places to take root. Crowd out weeds by planting vegetables and flowers in clusters, or growing big-leaved plants like zucchini.
Many ground covers also effectively choke weeds out. Just make sure it’s not a ground cover that becomes so rampant it turns into a weed itself, such as bigleaf periwinkle (vinca major).
For problem areas consisting only of weedy grasses and other weeds, King County noxious-weed expert Sasha Shaw recommends sheet mulching.
First cut down all the weeds. Then apply compost, water it in, and cover the area with cardboard or 4-6 sheets of newspaper. Overlap the edges by 6-8 inches, and water again. Finally, cover it with 3 to 5 inches of organic mulch such as chipped tree trimmings, or mixed straw and leaves. This sheet mulching should result in improved soil without the weeds, ready to be planted up in a few months.
Pulling weeds by hand seems like torture to some folks, but in recent years a variety of tools have become available that make manual weeding easier and more effective.
Many gardeners swear by the hori hori, a serrated weeding knife originating in Japan. The Weed Wrench, a long-handled puller that uproots large woody plants, “is murder on Scotch broom,” says Lisa Niehaus, a King County expert on alternatives to pesticides. A Dutch “corkscrew weeder” requires a little effort to learn how to use effectively, but it can pull out an entire dandelion root more than a foot long.
Find these tools and other innovative weed weapons at selected local stores or online. Try out various weeding tools by borrowing them, for a donation or membership fee, from one of the local “tool lending libraries” in Phinney Ridge, West Seattle and Northeast Seattle.
Other weed-busting strategies that don’t require synthetic chemicals involve vinegar, corn gluten or a propane torch. These methods may have downsides, from cost to ease of use, so research them carefully or talk to friends who have used them.
Noxious or invasive weeds common in local yards include English ivy, morning glory, blackberry and knotweed. Invasive weeds choke out shrubs and trees and take over large swaths of yards, parks, open spaces and roadsides.
King County’s Noxious Weed Control Program (206-296-0290) provides abundant resources for identifying and removing invasive weeds.
Whenever possible, pull problem weeds before they flower and go to seed. For many weeds, right now is the time to act. For other weeds it’s too late this year, but put a reminder on your calendar for next year.
If you decide to use a chemical product to deal with a major noxious weed problem, it’s important to exactly follow application instructions. Many people use herbicides incorrectly, which is dangerous and can make them ineffective. Always properly dispose of unused pesticides at a household hazardous waste collection facility.
Since weeds have been a source of inspiration for many writers and poets, let’s wrap up today’s weedy ruminations with a little original verse:
With vigilance and care
Control your noxious weeds.
But just make sure the cure
Is not worse than the disease