How to Prevent Nut Grass Before Vegetables

Get 'Em Young

• The sooner you begin weeding nut grass, the more you will be cutting down on its vigor. Even if you don't get the entire plant, the tubers will be weakened when forced to produce new foliage. Because nut grass tubers can be lodged 8 to 14 inches under the soil line, dig deeply into the soil with a hoe or garden fork to remove both the above- and below-ground portions of the plant -- ideally before it develops more than six leaves. Continue weeding every three weeks.

Dry Them Out

• Nut grass thrives in moist conditions. As you're preparing your vegetable bed, or watering adjacent beds, withhold as much water from the vegetable bed as possible. Drying out the area as a means of nutgrass control works best in combination with weeding. A repeated attack of uprooting the tubers and drying out the exposed ground underneath is effective for nut grass control before establishing vegetables in the plot.

Crowd Them Out

• Nut grass relies on full sun and lack of competition in order to grow and spread. If you have plenty of time to prepare your vegetable bed, use a cover crop to elbow out nut grass and other weeds. After you've uprooted as many young nut grass plants as possible, smooth the soil bed and sprinkle 1 ounce of white clover (Trifolium repens) or red clover (Trifolium pratense) for every 100 square feet of garden. White clover, which supplies nitrogen to the vegetable bed, can be planted the spring before a summer vegetable garden, or the fall before a spring or summer garden. It tolerates dry soil, so you can further keep nut grass at bay by denying the tubers water. Till the clover into the soil a few weeks before planting, or use it as a living mulch under larger vegetable transplants. Red clover is an annual crop. Both clovers thrive in U.S. Department of Agriculture plant hardiness zones 4 to 11.

Smother Them

• Landscape fabric can keep nut grass suppressed, but is most effective after you've used tilling, drying and other methods to eradicate the worst of it. The University of California's Integrated Pest Management program recommends using fabric made of polypropylene polymers. Flimsier mulches, such as those made from polyethylene, are too fragile to withstand nut grass' sharp blades. In vegetable gardens, plastic mulches don't work for direct-seeding. Save them for beds in which you'll be transplanting vegetable seedlings, cutting holes in the plastic as you transplant the seedlings. A straw, leaf or bark mulch set over the plastic can make the bed more attractive.