Pensacola News Journal

For:  Saturday, Jan. 29, 2005

By:   Daniel E. Mullins

        Extension Horticulture Agent

        Santa Rosa County

 

Don’t Wait Until Spring to Control Lawn Burweed

 

            A most aggravating weed exists in many Gulf Coast lawns.  It is commonly known as lawn burweed and locally as spurweed, with the botanical name Soliva pterosperma.  Where present it produces seed with burrs or stickers during the spring that seriously limit outdoor activities.  They will penetrate hands and knees when outdoors working and playing.  Walking barefoot across an infested area during April or May is out of the question.

            Good control of this weed species depends upon understanding its life cycle and applying control measures at the most vulnerable stage.  Too often control measures are sought after the burrs appear each spring.  At this point it is too late, as the weed has completed its life cycle. 

            Don’t confuse the sandbur with lawn burweed.  These two weeds are much different.  Sandbur is an upright growing summer grassy weed, bearing its spur covered seed pods on terminal spikes.  Lawn burweed on the other hand, is a spreading, low growing broadleaved winter annual.

            Lawn burweed germinates during late summer and fall.  It is present all winter in infested lawns, but is small and goes mostly unnoticed.  As February approaches it begins to grow rapidly, with closely spaced seedlings forming a mat about an inch high.  By April it has completed the vegetative or growth stage and begins to flower and set fruit.  It is the fruit, or seed, that produce the painful burrs.

            As with many other gardening activities, timing is everything when controlling lawn burweed.  There are two opportunities during the year for dealing with it.  At this time of year, burweed is already up and growing, so the goal is to get rid of it before there is an opportunity for seeding.  A few scattered plants can be pulled up and discarded.  Where lawn areas are heavily infested, it might be more practical to spray with a post-emergent broadleaved weed killer.

            Early to mid-February appears to be the most ideal time to use a post-emergent herbicide on this weed.  By then, it is in active growth and will readily take in the spray.  The amount of control will decrease with a later application because as the plant changes to the reproductive or flowering stage the weed killer is not as active.

            Good control of emerged lawn burweed is possible by using a mixture of 2,4-D, dicamba and MCPP.  Products are available that have these three herbicides combined, so there is no need to purchase them separately.  These include Trimec®, Ortho®  Weed-B-Gon for Southern Lawns/Formula II, Spectracide®  Weed Stop and Bayer Advanced® Southern Weed Killer for Lawns.  There are also other companies that offer a similar product under their brand names.

            Be careful using these mixtures on St. Augustinegrass or centipedegrass as they can be injured under certain conditions.  Choose a formulation similar to these that is recommended for your specific kind of lawn grass.  Label directions for these products are very specific.  Follow them exactly and be sure to treat in February before the stickers develop.  Repeat applications spaced 10 to 14 days apart are sometimes necessary for best control.

            The other opportunity for controlling burrweed is in late summer or early fall.  This involves applying a pre-emergent herbicide to prevent the seedlings from developing from seed.  I plan to provide an article on this subject in the summer.

 

 

Lawn burweed as it appears in late January. 

Control measures should be applied before it begins to flower and produce burrs.