GARDEN COLUMN FOR THE SALISBURY POST

Darrell Blackwelder

March 30, 2005

Warm weather and steady rain has made my grass and unfortunately, a host of weeds, grow at an incrediable rate. I applied a postemergence herbicide in an effort to effectively control the problem. I  can recognize results in just two days after application.

Postemergence herbicides are designed to control weeds after they have emerged.  Broad leaf weeds such as chickweed, henbit, clover, wild garlic, dandelion and others examples of broadleaf weeds controlled by postemergence herbicides.  There are a few herbicides on the market claiming to control crabgrass and other grassey weeds after they have emerged, however, sucess with these herbicides are somewhat limited.

     Broadleaf weeds are fierce competitors for space, sunlight, water and nutrients. Competition by employing by employing sound cultural practices. Vigorous and healthy lawns discourages both winter and summer weed growth, therefore, weed problems are generally symtomatic 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 grasses to a height of three and a half to four inches.  Shade from the turf discourages weed seed germination, especially crabgrass and dandelion.

     Broadleaf winter weeds have emergeed in most lawns after the  warm weather. 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 weed so far,followed by henbit, wild garlic(some refer to as wild onions) and dandelion.

     These weeds may be controlled with applications of a post‑

emergence herbicide. Most broad leaf 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.  Both systems work well for broadlead weed control. Many prefer the disposable hose-on, ready mixed applicators because of the simplicity which eliminates the concerned about pesticide storage.  Simply attach to your garden hose, spray and toss the empty container in the garbage.

     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. The problem facing now homeowners is many of the winter weeds have achieved excessive growth and are difficult to control.

     Broadleaf postemergence herbicides also are sold as granular

formulations or impregnated on fertilizers. Fertilizers with herbicides are more convenient and easier to apply than liquid herbicides but are somewhat pricy.  Also, fertization of cool season turf is only recommended for the early spring and fall. 

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e mail Darrell_Blackwelder@ncsu.edu