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By Tom Woods
There are two weeds found in lawns that have sharp burs: burweed and spurweed. It’s easy to get them confused, since their names are often used interchangeably, but there are ways to tell the difference, which is important since correct identification of a weed is the first step in controlling it.
Burweed (Soliva pterosperma) is also called spurweed, sandbur and sandspur. It is a winter annual broadleaf weed that grows prostrate (flat along the ground), reaching a height between three and four inches. The plant germinates in the fall and remains small throughout the winter. About the time spring sports start, Burweed has a period of rapid growth. It is during this growth spurt that the plant forms its spine-tipped burs.
Like most weeds, burweed invades thin turf. Because of its prostrate growth habit, it is not affected by mowing, unless you cut your grass to within one-half inch of the soil line, which can result in weakening your grass (making it more susceptible to weed invasion), if not killing it.
The best time to control burweed is before it germinates. Use a pre-emergent herbicide such as Atrazine in the fall or, if the plant has already started to grow, a post-emergent. For post-emergent control, you can use a two or three-way mix of 2, 4-D dicamba and MCPP. Other herbicides that control emerged burweed include: Weed-B-Gone, Trimec, Spectracide, Bayer Advanced Weed Stop and Southern Weed Killer. Be sure to read the manufacturer’s label and directions before use. You may need to reapply two to three weeks after the initial application.
If burweed has already developed the burs, reconsider before spraying. The plant will die as temperatures approach 90 degrees and secondly, the herbicide will kill the plant, but the burs will remain until they decompose. So at this point, you aren’t really taking care of the problem. This is why it is essential to spray before the plant starts developing the burs.
Sandbur (Cenchrus incertus) is a summer annual native to the United States. This rough-bladed plant is a common indication of sandy or light textured soils. The seed head of sandbur is a spike of tiny spurs, which is the easiest way to identify it. Like burweed, once the spurs have been produced, it’s really too late to control the plant.
Apply a pre-emergent herbicide, such as Atrazine, before the weed seeds germinate (they germinate when the soil reaches around 52 degrees). One of the main reasons chemical control of annual grassy weeds fails is because the herbicide is not watered in thoroughly, so be sure to follow label instructions.
Pastora (nicosulfuron + metsulfuron methyl) has just received its label in North Carolina to help with weed control in established bermudagrass pastures and hayfields. Pastora will help with post-emergent control of a number of broadleaf weeds, as well as barnyardgrass, broadleaf signalgrass, sandspur and johnsongrass and suppression of crabgrass. Applications of Pastora may result in temporary yellowing or stunting of bermudagrass. There are no grazing or haying restrictions.
Sandspurs (also called sandburs) are usually noticed after they have set seed and someone has had an encounter with those nasty burs; however, the best time to control sandspurs is on the early spring when they are young and actively growing. The herbicide Vantage provides the best post-emergence control of sandspurs in centipedegrass.
Send your gardening questions or comments to: Brunswick County Master Gardener Column, P.O. Box 109, Bolivia, NC 28422, or call 253-2610. Enclose a self-addressed stamped envelope if requesting information or a reply. Answers may be printed in this column.