Garden News: OK to spray winter lawns

Green weeds can be really obvious in brown, dormant lawns. LSU AgCenter weed scientist Ron Strahan says it’s OK to spray lawns now with liquid herbicides to control those winter weeds before they become mature and start producing seeds.

Liquid atrazine tests best in winter weed trials and is good for winter weed control in lawns now through April, Strahan says. Atrazine controls weeds like annual bluegrass, white clover, chickweed, bedstraw and lawn burweed or sticker weed. The herbicide is good but not perfect.

The next best option after atrazine are herbicides that contain 2,4-D as one or more active ingredients.

Most consumer herbicides will also have dicamba and mecoprop and possibly carfentrazone as additional active ingredients.

“We usually call these weed killers ‘trimec’-type herbicides,” Strahan says.

Weed control with these trimec herbicides can be improved with follow-up applications two weeks after the initial application.

Avoid weed-and-feed products until the lawn greens up, Strahan says. They’re typically high in nitrogen fertilizer.

Nitrogen applied to lawns in late winter can cause grass to begin growing early, leading to frost injury and brown patch disease susceptibility.

As with all chemicals, be sure to read the label to find out what the chemical is supposed to do and how to use it properly.

You asked

“I have two queen palms that are about 12 feet tall. Before the freeze the limbs were nice and green. I put blankets over the trunk and base during the freeze. Now most if not all the limbs are brown. Did the freeze kill them?” — Blaine

“One of the more cold-sensitive palms planted in the Baton Rouge area is the queen palm (Syagrus romanzoffiana). They often die when temperatures get down to about 20 degrees.

Prune off brown fronds of cold-injured palms in spring and wait. Be patient. If no new growth has appeared by the end of July, the palms are dead and may be removed.” — Dan Gill

Got a gardening question? Write to GardenNews@agcenter.lsu.edu.