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Brock: Cut your grass, eliminate your weeds this month

Sunny days and spring breaks have got a lot of people looking at their lawns at length and in person… and many do not like what they see.

Grasses – that is, those we want to grow – are slowly beginning to green up. Weeds, meanwhile, are partying like it’s still Mardi Gras.

There are several things you can do to combat weeds, and they fall mainly into two categories. One is chemical control. There are herbicides you can use to kill existing weeds and other herbicides to prevent weeds from sprouting.

The other thing we need to think about is overall lawn health. While weeds do compete with desirable plants for water, fertilizer, etc., they tend to take over lawns that were not in great health to begin with.

A healthy lawn will make it harder for weeds to thrive.

The chemical part of the equation is not that complicated. We’ll sub-divide (bear with me) the chemical category into post-emergent and pre-emergent herbicides. If you’ve got broadleaf (non-grass) weeds that have already emerged from seeds (post-emerge), you can apply chemicals now.

FIRST you need to identify your weeds.

Chemicals like 2,4-D, dicamba, mecoprop or a combination (often sold as “tri-mec”) can kill most of our broadleaf weeds. Beware, because using products with 2,4-D can result in chemical burn and off-target drift in temperatures above about 85 degrees.

And these chemicals (available as granular or liquid) will NOT kill weeds like annual bluegrass and crabgrass. Atrazine is a good option for those plus some others, and it won’t tend to burn your lawn in hot weather. The main downside of atrazine is that it needs to be properly watered in.

Be aware that there are different herbicide rates for different lawn grasses. Make sure you use what’s appropriate for your St. Augustine, centipede or whatever you have so you can avoid “burning” it up.

If you have the “sampler pack” of grass species like most people, use the lowest recommended rate for the grass you most want to keep.

Pre-emergent herbicides are simpler; they kill weed seeds as they begin to germinate, or “emerge.”

They usually come in granular form, so you’ll spread them on your lawn and wait for rain. While their application now will save you from many warm-weather weeds, most winter weeds are already emerged.

A late summer application (September or so) will stop most cool-weather weeds. Another application in late January is best to control weeds like lawn burweed, annual bluegrass and others you may be seeing now.

Details on turf care can be found in the LSU Ag Center’s “Louisiana Lawns” fact sheet and “Louisiana Lawns Best Management Practices” booklet. It mostly comes down to fertilizer and mowing height.

April is the month we usually start fertilizing, assuming the grass has grown enough to need mowing twice. Mowing height will vary greatly depending on grass type.

St. Augustine wants to grow taller, while Bermudagrass can be “scalped.” Fertilizer rates will also differ for different grasses. Refer to the above publications or ask me for details.

If you want to know more about gardening, landscaping, or anything else horticultural, contact the St. John / St. James Parishes County Agent André Brock at abrock@agcenter.lsu.edu. Also, the LSU Ag Center’s website can be accessed at www.lsuagcenter.com with lots of user-friendly information, including this article.