By Darrell Blackwelder
For the Salisbury Post
SALISBURY — August is generally the month when weeds flourish in both lawns and shrub beds. However, with the weather as it is, there seem to be more weeds than normal.
Yellow nutsedge is a weed that seems to be almost impossible to kill, both in shrub beds and lawns.
Yellow nutsedge is a very difficult weed to control. Most think of the weed as a type of grass, but it’s actually classified as sedge, not a grass. The blades are triangular shaped and grow very rapidly, especially in the hot, humid weather that we’ve experienced over the past few weeks.
Unfortunately, yellow nutsedge forms tubers (nuts) at the tips of the rhizomes. During the growing season, plants spread by rhizomes or underground stems producing “daughter plants.” Yellow nutsedge begins forming tubers at the tips of the rhizomes maturing in late July to mid-August. Under optimum conditions, a single yellow nutsedge plant can produce as many as 7,000 tubers!
The tubers are just one method of reproduction. Most sedges spread by underground rhizomes. However, these nuts or tubers may remain dormant in the soil for up to 10 years.
Hand-weeding nutsedge is possible early in the season before rhizomes have formed. Unfortunately, most of the weeds have already started producing rhizomes or “nuts” and “daughter” plants. Once this occurs, hand-weeding usually results in breaking the stem below ground and a new plant quickly replaces the old one in a day or two.
Spot spraying with a systemic herbicide such as glyphosate (Roundup) will control the newly emerged nutsedge; however, the sprouts below ground generally continue to emerge and continue to be a problem.
Many landscape maintenance professionals prefer to use a post emergence herbicide with the active ingredient halosulfuron-methyl to control the weed. It’s often sold as Sedgehammer or other trade names in local garden shops and retail outlets. This herbicide controls emerged nutsedge and also leaves a residual herbicide layer preventing new nutsedge from emerging for about four weeks.
The herbicide can be tank mixed with glyphosate (Roundup) for directed sprays in landscaped or fallow areas. It is very important to use only nonionic surfactants with this product for best results, with no rainfall or irrigation for at least four hours.
Those with chronic nutsedge problems in flower and shrub beds should also consider a preemergence treatment in the early spring. Pennant Magnum, a preemergence herbicide, will only suppress yellow nutsedge. Weed scientists at N.C. State University reveal a more accurate term would be partial control. Shrub beds treated with a preemergence herbicide in the spring before germination will most likely need a second post-emergence application later. Unfortunately, some hand weeding in the early spring cannot be ruled out as method of control.
Darrell Blackwelder is the County Extension Director with horticulture responsibilities with the North Carolina Cooperative Extension Service in Rowan County. Learn more about Cooperative Extension events and activities by calling 704-216-8970 or online at:
www.rowanextension.com.
www.rowanmastergardener.com
rowan.ces.ncsu.edu