Q I am trying to avoid using chemicals on my lawn, but I am concerned about weeds. Does corn gluten control weeds and where can I find it?

A Yes. Corn gluten meal, a byproduct of commercial corn milling, poses no health risk to people or animals and is a nontoxic substitute for synthetic preemergence herbicides. It's a weed-and-feed product.

Corn gluten meal is a preemergence product for crabgrass and other pesky weeds, but it does not kill existing plants. Annual weeds that are already up and growing will not be killed, but most of the seeds they produce later in the season shouldn't sprout.

In addition, existing perennial weeds, such as quackgrass, plantain and dandelions, will continue to come back from one year to the next because their roots survive most winters. But corn gluten meal will keep their seeds from sprouting so the population of perennial weeds, particularly plantain and dandelions, will decrease.

Don't expect to see instant results with corn gluten meal. Proper applications will give better results year-by-year. By the fourth year, weed control should be good. You can enhance its effectiveness with an increased mowing height; test plots show that grass mowed at a 3-inch height had significantly fewer dandelions than plots mowed to 1 1/2 inches.

Apply corn gluten meal, available in powder or pellets, in late April to early May, in mid-August and again in mid-October. Spread evenly at the rate of 20 pounds per 1,000 square feet of lawn. Water lightly to activate it. The August application is important because it prevents seeds from weeds such as dandelions and chickweed from sprouting in the fall and getting a head start the following spring. A third application in October has been shown to promote an earlier spring green-up.

A potential problem with corn gluten meal is that extensive moisture and soil microbial activity can reduce its effectiveness. You can control the amount of water you apply right after applying the corn gluten meal, but you cannot control rainfall. If it is too wet while the weed seeds are germinating, the seedlings may recover and form a root. If it does not rain within five days of application, apply ¼ inch of water.

Because it contains 10 percent nitrogen by weight, corn gluten meal doubles as a slow-release organic fertilizer. By applying corn gluten meal at the recommended rate, you are giving your lawn a total of 4 pounds of nitrogen annually, which is sufficient for your lawn's needs.

Corn gluten meal is available at nurseries and feed stores. Check the content label to find the corn gluten meal products.

Carl Hoffman, University of Minnesota extension horticulturist for Benton and Stearns counties

Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-7032, or e-mail fixit@startribune.com. Past columns are available at www.startribune.com/fixit. Sorry, Fixit cannot supply individual replies.