Many homeowners put out pre-emergence herbicides in the fall to prevent most of these weeds from ever coming up, but it doesn’t always get them all. Nothing is 100 percent in control and pre-emergence herbicides don’t stop most perennial weeds.
The quicker you take control of these winter weeds the better, for a number of reasons.
First of all, younger weeds are much easier to control than larger, mature weeds. The older a weed gets, the harder it is to kill. Larger weeds are more likely to need several applications of herbicides to kill them, 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 weed control even more of a headache down the road.
The vast majority of herbicides that you can use to kill winter weeds caution against using them during spring green-up of your lawn. The risk of injury from post-emergence herbicides is greater during the green-up process than when the turfgrass is dormant or actively growing. Using them can also delay green-up in the spots you spray.
It’s best to scout your lawn and find out what types of weeds you have. The more common winter weeds you will encounter in the lawn are annual bluegrass (poa annua), wild garlic (most people call them onions), common chickweed, henbit, lawn burweed, vetch, Florida betony (the subject of last week’s article), dandelions, Carolina geranium and cudweed.
If you have small areas and don’t like to use herbicides, then you might just pull or dig up the weeds. For large areas of weeds this is usually not very practical.
Getting rid of winter weeds will provide your lawn with an advantage when it comes time to green-up. Without weeds, the grass does not have to compete for sunlight, nutrients and moisture and can get off to a better start in the spring.
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 (Weed B Gon, Weedstop, Weed Killer for Southern Lawns, etc.).
All of these products can be used on all four of the grasses we grow. Some will tell you to reduce the rate for certain grasses. 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 or the other herbicides if your lawn was newly planted in the fall or winter and didn’t have a chance to root down and become established.
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 winter weeds. This has been done with success on Bermuda and zoysia when it is a cold winter and they are fully dormant, but if there are any green stolons, you could cause some injury. Usually the injury amounts to nothing more than a slight delay in spring green-up in the areas you sprayed. All of our grasses, including Bermuda and zoysia, have some green in them now because of the warm winter so I would advise against spraying with Roundup. No matter how cold the winter, you never want to do that if you have St. Augustine or centipede.
Always spot spray your weeds during the winter when the temperatures are at least normal or above normal (upper 50s or higher). It also helps when we get a good rain just a few days before your application so that the weeds are well hydrated. Take control of winter weeds now so you won’t have to deal with them later on this spring.
REACH SID MULLIS, THE DIRECTOR OF THE UNIVERSITY OF GEORGIA EXTENSION SERVICE OFFICE FOR RICHMOND COUNTY, AT (706) 821-2349 OR SMULLIS@UGA.EDU.