Blackwelder column: Consider weed control now

  • Posted: Friday, February 22, 2013 3:15 a.m.
Ryegrass is a broadleaf weed that shows up in weak lawns.
Ryegrass is a broadleaf weed that shows up in weak lawns.

ALISBURY — Now is the time to consider weed controls in cool season fescue before warmer weather arrives in March. Research has proven that controlling emerging weeds now is much more effective than waiting until they excel in growth later this spring.

Post emergence herbicides are designed to control weeds after they have emerged over the top of existing lawns. Broadleaf weeds such as chickweed, henbit, clover, wild garlic, dandelion and others can be controlled by post emergence herbicides. There are a few herbicides on the market claiming to control crabgrass and other grassy weeds after they have emerged.


One unwelcome grassy weed that has adulterated new lawns this spring is annual ryegrass. Most premium fescue cultivars planted last fall will have small to moderate amounts of this weed in new plantings. There is no feasible method to control ryegrass in newly seeded lawns. Fortunately, ryegrass will die naturally in the summer as warm temperatures arrive.

Broadleaf weeds are fierce competitors for space, sunlight, water and nutrients. Competition can be reduced by employing sound cultural practices. Vigorous and healthy lawns discourage both winter and summer weed growth, therefore, weed problems are generally symptomatic of a lawn with issues related to either poor fertility or unsound cultural practices. Ironically, many weeds actually thrive on poor soils and adverse growing conditions.

One method of controlling weeds is to mow cool season fescue grasses at a recommended height of 3 1/2 to 4 inches. Shade from the healthy turf discourages weed seed germination, especially crabgrass and dandelion.

Broadleaf winter weeds have already emerged in most lawns with the warm weather experienced earlier this winter. Winter annuals germinate in late September when soil temperatures drop below 58 degrees and lay somewhat dormant during the winter until early spring. Chickweed seems to be the most serious lawn weed, followed by henbit.

These weeds may be controlled now with applications of a post‑emergence herbicide. Most broadleaf weed herbicides or “weed killers” contain a mixture of various herbicides, such as 2,4‑D and dicamba. Post‑emergence herbicides such as Trimec, Weed B-Gon, Spectrum 33+ and various other formulations are applied to existing weeds in turf without injury to the cool season turf itself.

Broadleaf herbicides are usually sold as liquid formulations and are applied with compression sprayers or hose‑on applicators. Hose-on, ready mixed applicators are becoming more popular because of the simplicity of usage and the elimination of pesticide storage. Simply attach the applicator to your garden hose, spray and toss the empty container in the garbage.

Admittedly, broadleaf winter annual weeds in bloom are difficult to kill. These plants generally do not absorb herbicides at this stage of growth. Broadleaf weeds should sprayed at an early growth stage; therefore the younger the weed, the easier to control with herbicides.

Darrell Blackwelder is county extension director Rowan County Center, North Carolina Cooperative Extension. 704-216-8970

www.rowanmastergardener.com

rowan.ces.ncsu.edu

www.rowanextension.com

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