Many homeowners put out pre-emergence herbicides in the fall to prevent these weeds from coming up, but it doesn't always get them all. Pre-emergence herbicides don't stop most perennial weeds.
Winter weeds remain relatively small from the time they come up in the fall through most of January and early February. But once the weather begins to warm in late February and March, they begin to grow quickly. This is usually when everyone wants to kill these weeds, because the lawn is just beginning to green up and the weeds stick out like a sore thumb.
But if you have winter weeds you want to control, you'd be better off taking action now or during the next three to four weeks instead of waiting another six weeks to two months.
First of all, younger weeds are much easier to control than larger, mature weeds. Larger weeds are more likely to need multiple applications of herbicides, thus costing more in time and money.
Mature weeds also mean seed heads develop on the plant. They can release thousands of weed seeds over your lawn, making control even more of a headache down the road.
The majority of herbicides that you can use to kill winter weeds caution against using them during spring greenup of your lawn. The risk of injury from post-emergence herbicides is greater during the greenup process than when the turfgrass is dormant or actively growing.
It's best to find out what types of weeds you have. The more common winter weeds in the lawn are annual bluegrass (poa annua), wild garlic (most people call them onions), common chickweed, henbit, lawn burweed, Florida betony, dandelions, Carolina geranium and cudweed.
If you have small areas of weeds, you might just pull or dig them up. For larger areas, this is usually not very practical.
The weeds and type of lawn you have determine which herbicide you should select. There are really so many different brand names that I can't list them all here. The two dominant ones for winter weeds are atrazine and products containing 2,4-D + MCPP + dicamba. Image is another good one, particularly for wild garlic. For annual bluegrass, atrazine works the best.
All of these products can be used on all four of the grasses we grow. Atrazine can be used only on dormant bermuda and zoysia. As always, thoroughly read the label before you make any applications.
When using atrazine, take precautions not to use it over the root zone of desirable ornamental plants. You also wouldn't want to use it if your lawn was newly planted in the fall or winter and didn't have a chance to root down and become established. And don't use atrazine if you plan to put out any grass seed in the spring.
Many of these herbicides are sold in fertilizer products called Weed-N-Feed. Don't use them now as it is far too early to be thinking about fertilizing.
The question always comes up about using Roundup for weeds during the winter. This has been done with success on Bermuda and zoysia when they are fully dormant, but if there are any green stolons, you could cause some injury. The advantage of using Roundup is that it will work quicker and better and eliminate the need for a follow-up application.
You definitely would not want to use Roundup on St. Augustine and centipede.
Always spot spray your weeds during the winter when the temperatures are at least normal -- in the mid- to upper 50s. It also helps when we get a good rain just a few days before your application so that the weeds are well hydrated.
REACH SID MULLIS, THE DIRECTOR OF THE UNIVERSITY OF GEORGIA EXTENSION SERVICE OFFICE FOR RICHMOND COUNTY, AT (706) 821-2349 OR SMULLIS@UGA.EDU.