Weed Management in Lawns

Hot Springs, Ark. – Weeds occur in every lawn, but they seldom become problems in well-managed, vigorously growing turfgrass. Proper site preparation and turfgrass selection before planting are essential to give a new lawn a healthy start. Once a lawn is established, poor maintenance practices that weaken it--such as improper irrigation, fertilization, or mowing--are the primary factors likely to predispose it to weed invasion. Activities that lead to compaction also contribute significantly to turfgrass stress, making it easier for weeds to invade. An integrated weed management program can reduce most weed populations to tolerable levels and prevent large, unsightly weed patches. Total eradication of weeds is not a realistic or necessary goal for most lawns; however, with good management practices, a lawn can be practically weed-free without the extensive use of chemicals.

WEED IDENTIFICATION

Identifying weeds and knowing their life cycles are essential to management. Three general categories of weeds may be found in lawns: broadleaves, grasses, and sedges. Take care to distinguish weedy grasses from similar-looking lawn grass species. 

The life cycle of weeds may be annual, biennial, or perennial. Annual weeds are most commonly identified as either winter/cool-season or summer/warm-season and survive only one season. If not controlled before they flower, they can produce seed that will sprout the following year. Biennial weeds survive for two growing seasons, reproducing vegetatively or by seed; however, seed is not produced until the second year. Perennial weeds survive many years, and though some may produce seed, many primarily reproduce vegetatively by creeping stems (stolons and rhizomes), tubers, or fleshy roots. Perennial weeds are the hardest to control once established.

IRRIGATION

Many lawns are watered incorrectly. Poor irrigation practices can weaken turfgrass growth, allowing weeds to invade. Annual bluegrass, crabgrass, dallisgrass, and nutsedge are just a few weed species that thrive in poorly irrigated lawns. To maintain a healthy lawn, uniform coverage is needed. Sprinkler heads that are broken, obstructed, or set too low or too high may not reach all areas of the lawn and can result in dry or dead spots in an otherwise healthy turfgrass.

In general, deep, infrequent irrigation will encourage healthy root growth. Light, frequent watering is only required when the turfgrass has just been planted and the root system is developing. Watering established turfgrass lightly and frequently creates a shallow-rooted lawn, making it less durable and allowing shallow-rooted weeds such as crabgrass to get the competitive edge. Ideally, turfgrass should be irrigated deep enough to penetrate the soil to a depth of 6 to 8 inches. Allow the soil to partially dry out between watering. The top 1 to 2 inches of soil should be fairly dry before water is applied again.

Water requirements vary among turfgrass species and also vary depending on climate, time of year, and growing conditions. As a general rule, warm-season grasses only need to be watered once or twice a week. Turfgrass growing on clay soils does not need to be watered as frequently as turfgrass growing on sandy soils.  Clay soils retain water longer than sandy soils; sandy soils dry out quickly.

MOWING

Each turfgrass species has specific mowing height requirements. Mowing some grasses too short can weaken the turfgrass and increase weed invasions. Alternatively, if some grasses are not mowed short enough, the thatch layer can build up, reducing water penetration and weakening the turfgrass.

Mow grasses more frequently when they are actively growing. A standard guide is to remove no more than one-third of the leaf blade at each mowing. If too much is removed at one time, it can take some time for the grass to recover, giving weeds a chance to invade. Lawns with weed invasions often appear uneven. Mow weedy lawns frequently enough to avoid this patchy appearance and prevent flower and weed seed formation. Be sure that mower blades are sharp enough so that the turfgrass is not damaged. If mowers are moved from weedy lawns to other lawns, be sure to wash off the blades to avoid transport of weed seeds. Avoid mowing lawns when the soil is wet, such as after rain or irrigation; moving a mower over wet soil can lead to compaction.

FERTILIZATION

To maintain a healthy lawn, follow fertilizing guidelines carefully. Do a soil test prior to the growing season. This is a free service through the Cooperative Extension Service.

THATCH

Regular thatch removal will help keep your turfgrass healthy and competitive with weeds. Thatch is a layer of organic matter (stems, stolons, roots) that develops between the turfgrass blades and the soil surface. A thin layer of thatch is normal and even beneficial; it can help limit weed germination.

HERBICIDES

If your lawn is properly maintained, herbicides will generally not be necessary. When they are needed, use them as part of an integrated management program that includes good cultural practices. No single herbicide will control all lawn weeds, and not all herbicides can be used on all lawn species. You must identify your weed problem(s) and turfgrass species before choosing an herbicide. For more information call our office at 501-623-6841 or email me at abates@uada.edu. 

Master Gardener Information

Master Gardener meetings are held on the 3^rd Thursday of each month at the Elks Lodge.  They’re open to the public and guests are welcome. For more information call the Extension Office at 623-6841 or 922-4703 or email Allen Bates at abates@uada.edu.   

EHC Information

Are you interested in joining an existing Extension Homemakers Club? EHC is the largest volunteer organization in the state. For information on EHC contact Jessica Vincent on 623-6841 or 922-4703 or email her at jvincent@uada.edu.

4-H Information

We have several 4-H clubs for our Garland county youth who are 5 to 19 years old.  For more information on all the fun 4-H activities that are available for our youth, call Linda Bates at the Extension Office on 623-6841 or 922-4703 or email her at lbates@uada.edu .

The Arkansas Cooperative Extension Service is an equal opportunity institution.

By Allen Bates
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture

Media Contact: Allen Bates
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
236 Woodbine Hot Springs AR 71901
(501) 623-6841
abates@uada.edu

The Arkansas Cooperative Extension Service is an equal opportunity institution. If you require a reasonable accommodation to participate or need materials in another format, please contact your County Extension office (or other appropriate office) as soon as possible. Dial 711 for Arkansas Relay.

Pursuant to 7 CFR § 15.3, the University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.