Although homeowners with large-scale gardens may need help, small vegetable plots can and should be a study in organic gardening – at least so far as weeds are concerned.
"Usually, mulching and hoeing are all that's needed. There's no reason to introduce extra chemicals into your home environment," said Chuck Marr, vegetable crops horticulturist for Kansas State University Research and Extension. "In fact, if a mulched plot is small enough, you also can keep ahead of weeds by hand-pulling. In that case, I'd judge which approach to take by whether my hoeing or hand-pulling causes the least disturbance for the vegetable plants' roots."
Unless they're also a state-certified applicator, homeowners basically have just two herbicides available for use on larger gardens, Marr said.
One kills weed seeds as they germinate. It has to go on the garden before the weeds come up or after they've been physically removed. This pre-emergence herbicide is trifluralin, which is sold under such trade names as Treflan, Preen, Miracle-Gro Garden Weed Preventer, Gordon's Garden Weed Preventer Granules, and Monterey Vegetable and Ornamental Weeder.
"As with all herbicides, you must read and follow label directions carefully. For example, you can safely use trifluralin on asparagus, but only before the spears emerge," Marr said. "Products may have the same active ingredient, but each may be approved for use with a slightly different list of crops."
The second garden herbicide available to homeowners is a post- emergence weed control named sethoxydim. It's sold as Poast, Monterey Grass Getter, and Hi-Yield Grass Killer.
"As some of these trade names suggest, sethoxydim only kills grasses," Marr said. "But, you can spray it directly over the top of many vegetables. The product labels list the allowable ones."