Lawn Care/Basics for Homeowners-Lawn Care/Weed Identification and Control/Weed Control/Turfgrass Cultural Control

Pull-behind Aerification Unit Source: Texas A&M Turfgrass Program

The first defense against weed infestation in turfgrass is to produce a dense stand of healthy turf. Quality turf can compete well with weeds and is best achieved by properly preparing planting soils, planting turfgrasses suitable for the given situation, and by using standard cultural practices (mowing, watering, fertilizing, and cultivating).

Primary to any turf management program is properly selecting the turf to be used. For the golf course manager, this is generally not a problem area; there is a limited choice of turfgrasses appropriate for use on greens, tees, and fairways. Golf course turf selection is usually dictated by the desired quality, budget, and amount of play, not primarily by a desire to keep weed populations to a minimum.

Aerifier with Hollow Tines Source: Texas A&M Turfgrass Program

In any turf setting, following proper turfgrass selection, the second line of defense against weed and pest invasion is the use of correct mowing, irrigating, fertilizing, and cultivating practices. Proper mowing is critical to turfgrass health and appearance. Turfgrasses mowed too short become open, inviting weed invasion. Also, when mowed too short, turfgrass may develop inadequate root systems that allow plants to more readily succumb to insect and disease pests. When allowed to grow too tall, turfgrasses can appear unkempt and coarse-textured. Golf course playability is also altered when turves are allowed to grow tall. Basic mowing recommendations include frequent mowing at the tallest height recommended for the specific turf and use.

Irrigating turfgrasses is also important. Over-watered turf may grow too rapidly, develop shallow root systems, and be prone to invasions of weeds, insects, and diseases. Under-irrigated turf may become open and sparse, develop a poor appearance, and also allow weed invasions. Under most circumstances, when watering, water infrequently and deeply to the depth of the root system. When irrigated lightly and frequently, weed seeds (especially those of annual weeds) can germinate and readily develop into mature weeds because the soil surface is never allowed to dry out.

Fertilizers maintain turfgrass density, vigor, and color. Inadequate nitrogen fertilization leads to open turf that is readily invaded by weeds. Inadequate amounts of other minerals in the soil, especially potassium, phosphorus, iron, and sulfur, can also reduce turf color, disease resistance, and stress tolerance. Conduct soil tests and supply these elements as recommended by test results. It is important, however, not to supply excessive amounts of phosphorus to established turf. Excessive amounts of phosphorus at the soil surface can encourage development of germinating weed seeds.

Vertical mower blades slice through the turf to a specified depth increasing air and water flow to roots Source: Texas A&M Turfgrass Program

Cultivation activities include core aerification, slicing, and vertical mowing. These activities can reduce thatch and prepare turf for overseeding. Core aerification is also useful for reducing soil compaction. Conduct cultivation activities during periods of active growth when turfgrasses are best able to recover from these practices. In areas where annual weeds are a particular problem, conduct cultivation activities during autumn.

Insect pests and disease pests can thin and weaken turves, allowing weed invasion. Control these invaders by using good culture and the appropriate pesticides when necessary.

Excessive traffic physically damages turf and also compacts soil. Thin turf, prone to weed invasion, can result. Perennial ryegrass and tall fescues have the ability to tolerate wear better than most other cool season grasses. Where appropriate, use these grasses in high traffic areas. In addition, where possible, use lightweight mowing equipment and alter the equipment's path to spread wear evenly over the use area.

Compaction reduces the quantity of large, gas-containing pore spaces in soils. Some weeds (e.g., goosegrasses and knotweed) are more tolerant of low soil oxygen conditions than are most turfgrasses. Cultivate these areas so that the turf can better compete with weeds.

Along with compacted soils, other unfavorable growth environments can also create growing conditions to which weeds are more adapted than is turf. Shade that reduces light quantity and quality favors weeds (e.g., creeping charley and common chickweed) rather than turf. Prune or remove trees to allow more light to reach the growing area. this also can increase air movement and decrease disease problems. Excessively wet or dry soils also create environments in which weeds often grow better than does turf. If possible, provide external and internal drainage to move excessive water from the turf root zone. Also, supplemental irrigation can be used in dry periods. In general, try to create growing environments that favor turf and not weeds.

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