What is the No. 1 weed problem around the world? Nutsedges — and they are formidable foes.
Although commonly called nutsedge, the weeds don’t actually bear a nut, but they do produce small brown tubers with a nutlike appearance. There are two main types of nutsedges: yellow and purple.
Nutsedges are a nuisance because they grow upright rapidly, much faster than grasses. They can cover a large area in a matter of days.
They also are perennial weeds, coming back year after year and making it more difficult to control than typical annual weeds.
The main reason sedges are so difficult to control is because they can reproduce in more than one way.
While nutsedges produce seeds, they are often not viable, so the plants rely on underground tubers and rhizomes, which produce more tubers. This is called vegetative growth, and it is extremely aggressive in sedges.
Sedges can be identified by their triangular, upright stems; their triangular leaf blades; and purple or yellow flower heads.
The spikes of purple nutsedge are dark red to purple to a brown. In addition to yellow spikes, the yellow nutsedge produces gold or brown spikes with lots of flowers.
Nutsedges can be a sign that your soil needs help because they thrive in poorly drained and compacted soils.
The best way to control nutsedge is to be proactive. Make sure your grass is properly fertilized and cut to the right height regularly.
A healthy lawn with good drainage, loose soil and vigorously growing turf grass is the best defense and competition to the nutsedge.
Pulling nutsedge is often ineffective and may make things worse. To effectively control, you must remove the nut growing 6 to 12 inches below ground. If you pull young plants before tubers begin to form, hand pulling can be effective.
Cultivating or tilling nutgrass also is not recommended because it redistributes the rhizomes along with the tubers.
However, some research has shown that purple — not yellow — nutsedge can be controlled in summer by cultivating the affected area and withholding moisture, forcing the tubers to dry. However, repeated tilling and drying are required, and this will not be effective in areas where other plants need irrigation.
There also are chemical herbicides labeled for use on nutsedge with names such as Sedgehammer and Sedge Ender. Be sure to read and follow the manufacturer’s label.
For post-emergent herbicides that control both yellow and purple nutsedge, look for active ingredients halosulfuron, sulfosulfuron or imazaquin. For pre-emergent control of yellow nutsedge look for herbicides with the active ingredients metachlor and dimethenamid-p.
Contact herbicides will need to be applied more than once because it will kill the leaves in the first spray but tubers and rhizomes will remain active if you only make a single application.
Consult LSU AgCenter publication numbers 3624-LL and 3624-J for more information on herbicides and proper cultural practices such as cutting heights for specific turfgrasses. You can find these publications by searching for their numbers at LSUAgCenter.com.