Maintaining a healthy lawn by proper fertilizing, watering and mowing is your first line of defense in controlling weeds. However, if your lawn has become thin through neglect or weather-related reasons, you might need another level
of weed control. February is the time in northeast Texas to put out pre-emergent chemicals to control weeds and grasses. Pre-emergent herbicides control weeds by forming a barrier that prevents the seed from germinating.

First, identify the type of weed you need to control. Crabgrass, goosegrass, sandbur and dallisgrass are the major grassy weeds which cause problems in lawns during the summer. The first three are annuals that emerge from seed
each spring. Dallisgrass is a perennial that recovers from rhizomes in the spring, but also produces seed that spread throughout the lawn. With the exception of dallisgrass, these grassy weeds can be controlled with pre-emergent herbicides applied in late winter. Dallisgrass can be controlled by spot-treating the plants with a contact herbicide.

Broadleaf weeds such as dandelion, chickweed, henbit, clover, dock and mustard can be controlled with selective postemergent herbicides applied in the spring. These weeds can also be controlled by applying a pre-emergent
herbicide in the early fall (September). Only materials recommended for St Augustine grass and Centipede should be used on these lawns, as the turf might be damaged by some chemicals that are safe for Bermuda grass. Repeat
applications may be necessary for both pre-emergent and post-emergent herbicides. Label recommendations should be followed for all herbicides.

Marlan Thompson, former Smith County Master Gardener
Texas A&M AgriLife Extension Service


Winter weeds such as henbit, chickweed and annual bluegrass (Poa
) are common nuisances in lawns during spring. These weeds, along with many others, come from seeds that germinate in fall, grow slowly during winter and appear in early spring. They are unsightly in lawns and interfere with the growth and spread of grass. They die out when hot weather arrives leaving brown spots in the lawn. Pre-emergent herbicides are an effective way to control annual weeds. The herbicide kills seeds as they germinate so that weeds never emerge from the soil. However, pre-emergent herbicides are not effective against weeds that are already growing so they must be applied now to be present in the soil when germination occurs.

To prevent late winter/early spring annual weeds, apply a pre-emergent herbicide in early September (in northeast Texas).

Pre-emergent herbicides for home lawns are most readily available in granular form and can be applied with a fertilizer spreader. For uniform distribution apply the granules at half the recommended application rate while walking north and south across your lawn, and the other half walking east and west. After applying, thoroughly water the herbicide into the lawn. The herbicides are formulated to remain in the top portion of the soil, even after a heavy rain. Before applying pre-emergent herbicides be sure to read and follow the product directions carefully.

Tom Russell, former Smith County Master Gardener
Texas A&M AgriLife Extension Service

Posted in Turf Maintenance