Yellow nutsedge becomes prominent in pastures during hottest part of year

Yellow nutsedge (Cyperus esculentus) is a troublesome, difficult-to-control weed that is becoming more common in our pastures. Livestock don’t tend to eat it. It is also called chufa, nutgrass or watergrass.

It is important to remember that yellow nutsedge is neither a grass nor broadleaf weed, but a sedge. Understanding this plant’s biology makes it easier to know how to best control it.

Yellow nutsedge is a perennial plant that reproduces primarily by small underground tubers — called nutlets — which form at the end of underground stems called rhizomes. A single plant can produce hundreds of these tubers during the summer. Yellow nutsedge also can spread by rhizomes.

Yellow nutsedge produces a seedhead when unmown, but its seeds rarely germinate. Yellow nutsedge actively grows during the heat of summer when cool-season turf grows more slowly.

It typically emerges (germinates from tubers) a few weeks after crabgrass germinates and grows actively until the first frost in autumn.

A frost will kill the plant’s aboveground portion but the tubers will survive and overwinter in the soil. Dormant tubers can germinate and emerge throughout the following season or survive in the soil for more than three years.

Yellow nutsedge is most noticeable right now because its leaves grow more rapidly than the turf during the hottest summer months and it’s a lighter shade of green than most grasses. During spring and fall when it is cooler, nutsedge growth is slower and not as easy to spot.

Yellow nutsedge can be identified by the triangular shape of its stem. You can feel the shape by rolling the stem in your fingertips. Yellow nutsedge leaves are arranged in groups of three (three-ranked), which also distinguishes it from grasses.

The leaves are light green to yellowish and each leaf has a long, tapered tip. Each leaf also has a prominent midrib and has a slick, shiny or waxy appearance. While many grasses such as crabgrass have hairs on the leaf blades, yellow nutsedge does not.

Yellow nutsedge is a problem in many agricultural fields and in lawns that have been converted from farmland. It also is a troublesome weed in horticultural and nursery crop production.

People and equipment can spread yellow nutsedge by moving or disrupting the soil. The best method for controlling yellow nutsedge and many other weeds is to grow a healthy, dense, vigorous stand of turf that can compete with weeds. Encourage dense stands by following proper maintenance practices, including fall fertilization, not mowing too short and over-seeding/reseeding as needed.

Yellow nutsedge tends to be problematic in areas that are mown too short and it thrives in areas where soils remain moist from poor drainage or overwatering. However, yellow nutsedge also can be a problem in well-drained areas, especially in thin stands.

Sedges are problem weeds and difficult to control. There are herbicides available for sedge control but proper herbicide use and application timing is critical to optimize control. They are also a little on the expensive side and aren’t very effective on other problematic weeds.

For best results, apply herbicides prior to tuber production. The most common mistake is to apply herbicides too late in the season after yellow nutsedge is big, spreading by rhizomes and producing tubers. To be effective, you will need to implement a sedge control program early in the season and continue it for more than a year to reduce tuber populations in the soil and prevent the spread of this problematic weed.

Source: Aaron Patton and Dan Weisenberger, Purdue Agronomy.

For more information on herbicide options or cultural practices for nutsedge control, contact the Hardin County Extension Service at 270-765-4121 or [email protected].

MEETING CALENDAR• The Hardin County Cattlemen’s Association membership meeting begins at 6:30 p.m. Thursday at the Hardin County Extension Service office. Dr. Greg Halich will be presenting his research and thoughts on bale grazing. A meal will be served so please RSVP no later than Aug. 30 by calling the Hardin County Extension Service at 270-765‐4121.

• A Hardin County Agriculture Development Council meeting is set for 6:30 p.m. Sept. 7 at the Hardin County Extension Service office.