A typical question I get this time of year is this: “I’ve got weeds in my lawn. What kind of weed killer do you recommend?” I usually respond with a couple of questions: What kinds of weeds are growing in your lawn? Are you managing your lawn properly?
Weeds often appear in thin or weak stands of grass. Growing an unadapted grass or improperly mowing, watering and fertilizing your lawn will invite weedy invaders. Other pests and conditions that affect the health of your lawn, such as insects, diseases, compacted soil and thatch, will give weeds a competitive edge over lawn grasses.
Many weeds are fairly reliable indicators of growing conditions. For example, acid or low pH soils support an abundance of sorrel or sour grass. This weed is a close relative of the salad herb, which has larger leaves and a more refined lemony taste.
Compacted soils tend to favor goosegrass, prostrate knotweed, prostrate spurge, annual bluegrass, common chickweed, mouse ear chickweed and rushes.
Low fertility favors legumes such as white clover and black medic, as well as carpetweed, poorjoe, quackgrass, sorrel, yarrow, annual trampweed and yellow woodsorrel.
In damp, wet, poorly drained areas look for annual bluegrass, barnyard grass, common chickweed, ground ivy, mouse ear chickweed, moss, pennywort, rushes, sedges, speedwells and violets.
The secret to reducing the abundance of any of these weeds is to change the conditions that favor their growth. Soil improvement, not an herbicide, is the best way to assure that your lawn grasses gets the upper hand. Improve drainage by adding organic matter or filling in low spots with native soil. Have your soil tested every three or four years and follow the recommendations from on the report. Maintaining the appropriate soil pH (generally between 6.2 and 6.5) and supplying only the minerals that are deficient will improve the growing environment for your lawn grasses. Warm-season lawns, such as centipede grass, bermuda grass, and zoysia grass, can be aerified at this time of year. Aerification loosens compacted soil and increases the availability of water and nutrients. It also enhances oxygen levels in the soil, stimulating root growth and enhancing the activity of thatch-decomposing organisms, thereby enhancing thatch breakdown.
Information about these and other lawn maintenance practices that will help your lawn naturally outcompete weeds for light, water, nutrients and space can be found at the Clemson Extension Home & Garden Information Center (http://www.clemson.edu/extension/hgic/).