Controlling Sedges in Turfgrasses

Fred Yelverton
Extension Crop Science Specialists- Weeds
Crop Science Department, N. C. State University

HTML Version (SCH): July 31, 1995

Have you noticed that sedge and/or nutsedge problems seem to be worse this year? There is a good explanation why this may be the case. Sedges are usually more of a problem in wet soils and can most often be found around areas that stay wet, such as around sprinkler heads or areas that do not drain well. With excessive rains during June over much of the state, sedges have thrived and many people are reporting that they have observed them in places not previously seen.

Most of the time, sedges exist in patches within turf but on occasion they can infest large areas. Sedges have traditionally been one of the more difficult family of weeds to control. With the advent of new herbicides over the last several years, control is much easier now but these weeds remain as some of the more difficult to control.

When sedges are discussed, the conversation usually centers around two perennial species; yellow nutsedge and purple nutsedge. In traditional field crops, a sedge problem will almost always be either yellow or purple. However, in turfgrasses, it is much more common to find sedges that are neither yellow nor purple nutsedge. In North Carolina, there are 41 species of sedges. Many of these are annuals but most are perennials. Most species inhabit waste areas such as ditches or areas that are not maintained. However, of these 41 species, probably about seven or eight can be commonly found in turfgrasses. The most common species found in turf is still yellow nutsedge. Purple nutsedge and some of the annual sedges are fairly common as well. Cylindric sedge and Texas sedge are less common but can be found, and in the southeastern part of the state, green kyllinga can be found. Green kyllinga is perennial sedge and is common in turf in the southeastern coastal area and in states south of North Carolina. Green kyllinga is more difficult to control than either yellow or purple nutsedge.

It is important to know which sedge you have because herbicides differ in control of the different sedge species. Herbicides registered for control of nutsedge usually control either yellow nutsedge (i.e. Basagran T/O controls only yellow) or yellow and purple nutsedge (i.e. Both Manage and Image control yellow and purple). It is difficult (with some species it is impossible) to differentiate between the sedge species prior to the development of a seedhead. Under mowing conditions, seedheads will not develop unless it is one of the low growing sedge species (Green kyllinga is sometimes an exception. Seedheads can often be found even under low mowing conditions). If a mowed area is infested with a sedge, I would suggest the following methods to help correctly identify the species:

• Look over in a fringe area that is not being mowed. Often times in nutsedge infested areas, there are a few plants growing in a border area that do not get mowed regularly that may have a seedhead, or
• Dig up a sedge plant and either place it in a pot or replant it in an undisturbed area so it can produce a seedhead.

Once a seedhead has been produced, a positive identification is possible. You can try to identify it yourself, or you can take it to your local County Cooperative Extension office in which case they will send it to me for identification if they are unable to identify the species. You may send it directly to me if you so choose.

A seedhead is not always necessary to differentiate between yellow and purple nutsedge. One way to distinguish these two is to dig up the tubers and peel the outer part back with a knife. Cut a nice little clean chunk out of the tuber and taste it. If it is very sweet, it is yellow nutsedge. If it is very bitter, it is purple. This may sound a little bizarre (so do not let anyone see you do this) but it is a definitive test for yellow and purple. Another less reliable way to distinguish between yellow and purple is to look at the leaf tips (this may also require growing it out). Yellow nutsedge leaf tips gradually taper to a sharp point whereas purple nutsedge tapers very abruptly and has the appearance of a blunt tip.

The obvious reason to go to the trouble for a correct identification is because of the difference in sensitivity of herbicides to the various nutsedge species. For instance if you have yellow nutsedge, bentazon (Basagran T/O or Lescogran) will provide good control and is considerably less expensive than some of the other newer herbicides. Basagran T/O (or Lescogran) or MSMA will control some of the annual sedges. However, Basagran will not control purple nutsedge. Pennant can be applied for preemergence control of yellow nutsedge but, like Basagran, will not control purple nutsedge. There is a considerable amount of interest among turfgrass managers in a new herbicide called Manage. Manage 75DF is a good sedge material that provides control of both yellow and purple nutsedge. It also gives some suppression of green kyllinga. The performance by Manage on some of the other species of sedges is unknown at this time. It is also a relatively expensive herbicide. If you have some species other than yellow, purple, or kyllinga, Manage may not provide control.

Regardless of which herbicide you use, at least two applications will be necessary for complete control, particularly if the sedge infestation is very heavy. It is necessary to first obtain a positive identification of the species if control measures are to be effective and the most economical.

The following is a list of nutsedge materials and their sensitivity to the various turfgrasses.