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Yellow Nutsedge

Looks like grass but is actually a sedge

By: Sandy Feather ©2009
Penn State Extension


Q. Yellow nutsedge is a recurring problem in my lawn. I have done some research, and even used recommended herbicides, but I cannot seem to get rid of it. Do you have any suggestions?

A. Yellow nutsedge (Cyperus esculentus) is a common weed in lawns and ornamental beds, especially in moist or wet areas. It is easy to identify by its lighter yellow-green color and the fact that it usually grows faster than the surrounding lawn grasses. Yellow nutsedge also produces bristly, chestnut brown seedheads that resemble small bottlebrushes when it is not mowed. It is not a true grass, but a sedge, characterized by erect, triangular stems.


Identification Help:
'Sedges have Edges'

A commonly used mnemonic device to help students remember the difference between grasses and sedges is "sedges have edges."  If you pull out a stem and cut it in half, the stem is visibly triangular in cross section.


One tough customer!

Yellow nutsedge can be difficult to control because it grows from underground tubers (also called nutlets) that provide a steady supply of carbohydrates. The top growth pulls up rather easily, but the tubers usually remain behind in the soil. Yellow nutsedge quickly re-sprouts from the tubers. If you pull it out relentlessly, you would eventually exhaust those carbohydrate reserves and get rid of it. However, it is likely to exhaust you or your patience before then.

 


Herbicides for Controlling Nutsedge

Professional use products such as Manage (halosulfuron) or Basagran (bentazon) provide the most satisfactory control. These products are not restricted use, but are not usually available to home gardeners. Bentazon is sold to home gardeners under the trade name Monterey Nutsedge ‘Nihilator (if you can find it locally), and Manage is available in single-use blister packs from some commercial turf supply dealers. These are selective herbicides that provide good control of yellow nutsedge without harming desirable lawn grasses when used according to label directions.

yellow nutsedge
Yellow nutsedge looks similar to grass, but has a
wider glossy leaf and a triangular shaped stem

However, timing is everything. These products are most effective on small plants. For example, label directions recommend applying Manage as soon as the weeds reach the three to eight leaf stage, prior to blooming. It is usually necessary to make a second application six to ten weeks after the initial one, once plants that have re-grown reach the three to eight leaf stage. After tubers form in late summer, herbicide applications are much less effective. It would be better to pull it out by hand at that point, and save your herbicide applications until the following spring.

It is also important to add a non-ionic surfactant to your spray tank (one-third fluid ounce per gallon). Non-ionic surfactants are products that help herbicides penetrate the waxy cuticle of weeds such as yellow nutsedge. Manage will not be nearly as effective if you do not use the non-ionic surfactant because less of it will be absorbed into the weeds. You may need to make applications next year to get complete control of this tough perennial weed.


Cultural Controls for Nutsedge

It is helpful to integrate cultural practices with chemical controls to gain control of hard-to-kill weeds such as yellow nutsedge. Practices that encourage a dense, thick lawn will help the grass outcompete the yellow nutsedge. Have your soil tested to ensure that you are fertilizing properly and that your soil's pH is in the optimum 6.5 - 7.0 range that most grasses prefer. Be sure to water deeply and infrequently to help the grass develop a deep, extensive root system. Since yellow nutsedge prefers a moist or wet environment, make sure that the soil drains adequately in those areas.

A quick test is to dig a hole 18 to 24 inches deep and fill it with water. Time how long it takes for the water to drain. If it drains in an hour or two, drainage is not a problem. If the water stands in the hole for more than five or six hours, you have a drainage problem that may require French drains or other measures to move water away from the area. Make sure that you are not overwatering that area when you water your lawn. Finally, raise your mowing height to between two-and-a-half and three inches. If you cut it shorter, you reduce the lawn’s root system and its ability to outgrow weeds of all kinds. Leaving your lawn a little taller makes for a healthier lawn, and allows it to shade out competing weeds, too.


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