Scott Eckert: Why weeds invade lawns

Scott Eckert

Ask homeowners about their No. 1 lawn concern, and the usual reply is "weeds.” But most homeowners are too narrow in their approach to controlling weeds.

When someone asks, “How do I control weed X?” they usually mean, “What product do I spray?” Although herbicides are an important tool for controlling weeds, they are only a part of a total weed control program. The best defense against weeds is a dense, healthy, vigorous lawn, which can only be obtained through proper fertilizing, watering and mowing.

Performing lawn care tasks take time and care. Still we water and fertilize like we think we should but we still end up with weeds. Here are factors and conditions that favor weeds.

Improper mowing. Mowing too low and too infrequently thins the turf, allowing weeds to get started.

Improper watering. Frequent watering encourages weed seed germination, disease, thatch and a shallow-rooted turf that is less competitive with weeds for soil moisture and nutrients.

Improper fertilizing. Fertilizing too much, too little or at the wrong time may benefit weeds more than grass.

Insect and disease injury. Weeds rapidly invade lawn areas that are thinned by insects and diseases.

Compacted soil. Soil compaction is a hidden stress on the turf grass root system. The grass is unable to compete effectively with weeds. Clay and silty soils are especially prone to compaction.

Excessive wear. Turf areas that are used for recreation and sports are subjected to wear and compaction. Weeds become a problem in these areas, requiring intense weed control and turf management.

Wrong kind of grass. The wrong kind of grass for the location will gradually decline and be invaded by weeds.

Environmental stress. Weeds often take over a lawn after it has been weakened and thinned from weather-related stresses.

Thatch. Excessive thatch causes shallow-rooted grass and contributes to insect and disease problems, which are followed by weed invasion. Thatch also can reduce the effectiveness of some soil-applied weed control chemicals.

— Scott Eckert is a Kansas State Research and Extension agent for Harvey County. Horticulture is his specialty. He can be reached at 316-284-6930.