Lawn Care/Basics for Homeowners-Lawn Care/Weed Identification and Control/Using Weeds as Indicators

It is commonly thought that large weed populations are responsible for driving desirable grasses from a turf area. In reality, the presence of weeds, and the lack of turf, is often an indication of the turf's inability to compete and survive in settings where weeds can. Although it is impractical to expect totally weed-free turf, the presence of large numbers of weeds is often an indication of problems in the growing environment or in turfgrass culture. Employing recommended cultural techniques and altering the growing environment can improve turf quality and health and, thus, reduce the need for pesticide applications.

Reasons for weed invasion -- Large populations of weeds in turf are usually indications of:

• Improper turf selection
• Poor culture
• Insect pest or disease invasion
• Excessive traffic; or
• Unfavorable growth environment

Weeds specific to certain environmental and management conditions -- Often, the presence of specific weeds in turf provides clues to the type(s) of environmental and management problems. By learning about weeds that commonly occur under certain conditions, managers can more easily identify these problems and correct them. Table 1 presents various weeds that are indicators of problems.

Some weeds are not very specific as to the conditions necessary for invasion. For example, dandelions (Taraxicum officinale) and quackgrass (Elytrigia repens [Agropyron repens]) can occur in a variety of environmental or turf management conditions.

These lists may not prove to be true for every situation. For instance, yellow nutsedge, once established, can tolerate dry soils. This weed is, however, more commonly found in moist conditions, especially when first becoming established.

Use this list as a guide when diagnosing turf problems. It, along with knowledge of turf growth requirements, can be of assistance when determining needed changes in growth and management conditions that favor turf health and quality.

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