Lawn burweed is a winter annual weed that becomes problematic in spring. It is a low-growing weed with leaves somewhat resembling a miniature version of parsley.
Burweed seeds germinate in fall. The plants remain small and inconspicuous during winter. It’s not until temperatures warm in spring that this innocent-looking and often unnoticed weed begins rapid growth, forming spine-tipped burs in its leaf axils. These sharp, spiny burs hurt as children begin to use the yard again, running around barefoot on a nice early spring day. Even the dog playing fetch suddenly starts doing a painful dance as it finds its way into a prickly patch of burweed. This weed can make a lawn area useless until it dies away and decomposes in late spring or early summer, only to reappear from left behind seeds next winter. Individual plants can form a mat spreading to a foot or more in diameter.
Burweed can easily be controlled during winter months before the spiny burs become a problem and seeds are produced. But if you wait, you’ll have to put up with the pain and inconvenience until the burs again wither away.
December, January and February are ideal months to apply a herbicide for the control of burweed. Look for lawn herbicides containing atrazine, 2,4-D or dicamba. Centipedegrass and St. Augustinegrass have excellent tolerance of atrazine. Although labeled for use on most of our permanent lawn species, 2,4-D has been known to cause injury to St. Augustinegrass and centipedegrass, especially during periods of hot weather. Use lower rates of dicamba on centipede and St. Augustinegrass. Do not use these herbicides (especially dicamba) within the root zone of desirable landscape and garden plants, including trees. Always follow label instructions and precautions.
The key factor to effectively control lawn burweed is to apply an appropriate herbicide during the winter months.
The next plant clinic will be held Friday, April 8 from 10 a.m. to 1 p.m. at the Okaloosa County Extension Annex located at 127 West Hollywood Blvd. in Fort Walton Beach.
The plant clinic is designed to provide a place and time for people to bring in samples of plants for diagnosis including weeds for identification.
If you have a plant problem that you would like diagnosed, bring a sample of the weed, plant, insect, etc., to the clinic. Be sure to bring a fresh sample that represents what is seen in the landscape. This may include a plant stem with several leaves, a 4-inch square of grass with roots attached, etc.
You may also bring a sample of your soil for pH testing.
Larry Williams, UF/IFAS Extension Agent, Okaloosa County, March 31, 2016