Beginning in late April and continuing through May, I receive many calls from homeowners who, when walking barefooted across their lawns, feel the pain of a winter annual weed called lawn burweed (Soliva sessilis), a member of the aster family. It is also commonly called sticker weed, spurweed and sandbur. By that time of the year, its spines have already been produced; killing the weed in late April or May will not eliminate the spines.
The LSU AgCenter recommends applying herbicides from December – March to kill the lawn burweed and eliminate production of the sharp spines. Lawn burweed is a winter annual that sprouts in the fall and winter and remains rather small during the winter months. As spring arrives with warmer temperatures, this weed goes in to a reproductive stage which begins the formation of seeds and sharp spines as it approaches maturity. As I’ve stated in the past, the best way to prevent or diminish the invasion of weeds in any lawn is to maintain a healthy lawn that out competes weeds for water, nutrients, space and light.
However if your lawn has a history of sticker weed or lawn burweed, you should be able to identify it in your lawn now. Look for a green low growing weed with leaves resembling parsley. See the picture of lawn burweed, below, taken recently in my St Augustine lawn. Applying a post emergence broadleaf herbicide when our daytime temperatures are 60 degrees or above will control this weed. Either one of two herbicides, Weed B Gon Max for Southern Lawns by Ortho or Weed Free Zone by Fertilome, will give satisfactory control. The recommendation is to make an application, wait 10 – 14 days to evaluate its effect, and make a second application if needed.
It is recommended that no applications be made on windy days and that none of the herbicide come in contact with desirable bedding plant, shrubs or trees. Both herbicides are labeled for warm season lawns. If this weed is not controlled by mid–to-late-April, the spines will already be formed and anyone walking barefoot on the lawn will experience the pain of sharp spines.
Many people call and ask me if they could apply Weed & Feed to control lawn burweed.
Dr. Ron Strahan, of the LSU AgCenter, told me that he wouldn’t recommend Weed & Feed during the winter months because it contains fertilizer. Applying fertilizer to St. Augustine grass or any other warm season lawn grass during the winter months could aggravate brown patch disease or increase susceptibility to winter injury. Any fertilizer applications should not be made until early April.
It is extremely important to follow all label directions for the mixing and application of all pesticides. Remember that the label is the law and any time you use a pesticide in a manner that is inconsistent with its label you are breaking the law.
Hoping everyone had a happy and safe holiday season and I look forward to a very productive 2014 – HAPPY GARDENING!!!
Gerald P. Roberts