Integrate Your Approach to Weed Control in Home Lawns

Tim R. Murphy, Extension Weed Scientist

The first method of an integrated approach is to use cultural techniques that promote vigorous growth and development of an adapted species of turfgrass. Research conducted across the United States has consistently shown that properly maintained turfgrasses have less weed problems than turfgrasses that are improperly maintained. Cultural methods proven to decrease weed problems are:

Irrigate as needed during the growing season to maintain turfgrass growth. During their periods of active growth, turfgrasses require 1.0 to 2.0 inches of water per week depending upon the turfgrass species, air temperatures and soil types. Supplemental irrigation should be used during periods of drought; however, do not over irrigate. Excessive amounts of irrigation water promotes the growth of weeds such as purple nutsedge, green kyllinga, pennywort and many species of rush. Conversely not irrigating during periodic summer droughts promotes the growth of drought-tolerant weeds such as common lespedeza, the purslanes and goosegrass.

Fertilize and lime turfgrasses according to soil test recommendations. The different species of turfgrasses have unique fertility needs, particularly for nitrogen. For example, centipedegrass needs only 1.0 to 2.0 pounds of nitrogen per 1,000 square feet per year while hybrid bermudagrass requires 4.0 to 6.0 pounds of nitrogen per 1,000 square feet per year. Excessive applications of nitrogen over a period of years can be deleterious to centipedegrass. Under fertilization of bermudagrass will prevent this species from competing weeds. In Georgia, the recommended soil pH for all species of turfgrass is 6.0 to 6.5. Centipedegrass can tolerate soil pHs as low as 4.5; however, a higher pH is preferred. Low soil pH can reduce the availability of certain plant nutrients and the growth of turfgrass. When turfgrass growth is impaired, the ability of the turfgrass to compete with weeds is decreased. Your county Extension agent or lawn and garden store can advise you on soil testing.

Plant a turfgrass species that is adapted to your area. Georgia has widely differing geographical areas and local climates. Cool-season turfgrasses such as tall fescue do not do well in south Georgia. St. Augustinegrass, a deep-south warm-season turfgrass does not survive well in north Georgia. Additionally, the amount of shade present in lawn will influence turfgrass growth. The bermudagrasses perform poorly in shaded sites. In north Georgia, tall fescue would a good choice on sites with moderate shade. In south Georgia, St. Augustinegrass could be used on shaded sites. Alternatively, under dense shade, a shade tolerant ground cover such as liriope or English ivy, or other ornamentals should be used in lieu of turfgrasses.

Correct soil compaction and drainage problems in the lawn. Weed species such as annual bluegrass, goosegrass, common lespedeza and broadleaf plantain thrive in areas that have compacted soils. Turfgrasses will not properly grow in compacted soils. Core aeration relieves soil compaction, and improves air and water movement into the soil. Turfgrass growth is improved and the turfgrass is better able to compete with weeds.

Mechanical methods of control include mowing and hand removal. Recommended mowing heights vary among the different turfgrass species. For example tall fescue should be mowed at a height of 2.5 to 3.0 inches. Hybrid bermudagrasses, such as 'Tifway' are mowed at heights of 0.5 to 1.5 inches in home lawns. Mowing at the height recommended for hybrid bermudagrass thins outs tall fescue and actually promotes the growth of crabgrass and common bermudagrass. Turfgrasses should be mowed often enough so that no more than one-third of the leaf surface area is removed at any one time. On hybrid bermudagrass that is well fertilized and irrigated it can be necessary to mow as often as three times per week during the summer months. In contrast, with a slow growing species such as centipedegrass, it may only be necessary to mow every 7 to 10 days during the summer months. It is impractical to weed a lawn thoroughly infested with weeds. However, a small infestation of weeds can easily be removed by hand. Don't give that "strange-looking" plant time to develop into a major weed problem. Hand-remove before it has a chance to form viable seed.

Despite following all the recommended turfgrass maintenance practices it is usually necessary to use herbicides for weed control in lawns. However, view the level of control obtained with herbicides as supplementing the weed control obtained by using good turfgrass maintenance practices. Will herbicides used in the absence of following good maintenance practices provide a high, quality attractive lawn? No. Will good turfgrass maintenance practices control all the weeds in the lawn. No. It is a 1, 2, 3 strikes, "the weed is out" approach. By using this integrated approach the natural beauty of the turfgrass is able to develop in the absence of weeds. There are numerous herbicides available for use on home lawns. Your county Extension agent or lawn and garden center can advise you on the appropriate product, when to apply it and the expected results. However, remember - the integrated approach is the key to achieving the goal of a high quality, attractive area of turfgrass!