October 23, 2017
During late February to mid-April, homeowners bring in bags of winter annual weeds from their lawns wanting advice on how to control them. They usually seem disappointed and confused when I tell them that it’s too late to bother with controlling winter annual weeds during late winter to early spring. Standing there holding a bag of weeds and with a lawn full of weeds back at home and not satisfied with my comment, they follow with a statement and a question such as, “Well, my lawn is full of these weeds now. What can I do?” I tell them to just mow them and explain that they will completely die as a result of the warmer temperatures of mid-April and May.
At this point, looking a little frustrated, the homeowner may ask, “Is there something I can spray on my lawn to kill these weeds?” To which I reply, “Yes, but it’s pretty much a waste of time and money this late.” I then try to explain the lifecycle of winter annual weeds. The weed seed, which have been dormant during the hot summer months, begin to germinate in fall. The seedlings continue to grow through the winter, mature, produce flowers and countless seed. By late winter/early spring (when the homeowner is asking about control), these winter weeds are now at the end of their lives. They are almost done with producing seed and will die with the coming warmer temperatures of mid spring. Control should have been attempted at the beginning of their lives in October, not at the end of their lives during late February to mid-April.
If you’ve had a history of winter annual weeds in your lawn, the best option is to apply a preemergence herbicide during October. Done correctly, the application of a preemergence herbicide forms a chemical barrier along the soil surface preventing the winter annual weeds from emerging. This successfully breaks the lifecycle.
Timing of herbicide applications is of utmost importance in controlling winter annual weeds in lawns.
The preemergence herbicide needs to be applied during October when nighttime temperatures drop to 55° to 60°F for several consecutive nights. This will be just before the winter annual weeds emerge.
A second application may be required six to nine weeks after the initial application to achieve season-long control.
Follow label directions and precautions when using any pesticide, including herbicides.
Some of the more common winter annual weeds are chickweed, henbit, Carolina geranium, annual bluegrass, hop clover and lawn burweed.
With small infestations of weeds, perhaps hand removal is the easiest and cheapest way to control them.