Hawkweed (Hieracium spp.) often forms dense colonies in areas of the lawn where the soil is infertile and acidic. A hardy perennial found throughout North America, hawkweed holds its rosettes of wildly hairy leaves close to the soil surface, safe from mower blades. Orange hawkweed (Hieracium aurantiacum) and meadow hawkweed (Hieracium pratens) are invasive forms that send up orange or yellow, respectively, dandelion-like flowers on 12-inch-tall leafless stalks. Established plants send out shallow bud-bearing stolons, which form new plants. Dig colonies in spring, and promptly repair the spot with seed or sod. Apply lime if the soil's pH is below 5.5. Sites infested with hawkweed benefit from organic fertilizers, which help the turf grass grow stronger and crowd out the hawkweed.Weed Control Techniques
Digging. Weeds that regrow from persistent roots must be dug. Use a spade or digging fork to dig spreading perennials, such as bindweed, Canada thistle, and quackgrass. Start digging a foot away from the plant's center to loosen the soil. Then lift the weed from beneath, which reduces how many root pieces are likely to break off and regrow. Dandelion, dock, and other weeds that grow from persistent taproots can be dug the same way, or you can use a special fork-like tool called a dandelion weeder to pry them up. Dig very large taproots that are difficult to pry loose. In lawns and other places where digging dandelions is not practical, use a sharp knife to slice off the leaves and the top inch or two of taproot at a diagonal angle. Some weeds that are easily pulled when the soil is moist must be dug from dry soil.
Crowding plants. When plants grow so close together that the ground between them is shaded, sun-seeking weeds, such as pigweed and purslane, don't have a chance. Use double rows rather than single ones whenever possible in your vegetable garden. In flower beds, place flowers in closely spaced groups. As plants need more room to grow, thin them gradually so weeds get only a fleeting chance at good light. Plants with broad leaves, such as squash and cabbage, do a good job of crowding out weeds. Vigorous lawn grasses that form a tight turf naturally crowd out weeds. To keep turf tight, apply a slow-release organic fertilizer during your lawn's most active season of new growth. The recommended cutting height varies with different species of grass, but with any type of grass it's a good weed-preventive strategy to mow high and often. Long blades of grass often do a good job of shading out germinating weed seeds.Photo courtesy of Plant Stock Photos