Nutsedge in Lawns

June 6, 2015

Nutsedge in Lawns

As if I haven't had to mow my lawn often enough this year, every three days or get out the bagger... which I don't like to do. When I mowed my lawn last week, I noticed a few clumps of lighter yellow grass that were a couple inches taller than the surrounding turf. Immediately I knew what I was up against.

Yellow nutsedge is a member of the sedge family although it closely resembles a grass. In fact it is frequently called nutgrass or watergrass. It's a common weed in lawns and landscapes, and can often be found in areas with moist soil. Yellow nutsedge is a perennial plant, meaning that the below ground portion of each plant survives the winter and generates new top growth each spring.

When you look at it closely, yellow nutsedge has a unique form and is easy to distinguish from turfgrasses and other grassy weeds. The leaf blades are light yellowish-green and are "V" shaped with a prominent ridge down the center of the leaf blade. These leaves originate from the base of the plant giving the lower stem a distinctive triangle shape.

The root system is shallow and fibrous, often producing small nut-like tubers that serve as food storage organs. These small tubers can sprout and form new plants. The plants also spread by rhizomes, or underground stems, which enables it to move rapidly throughout a lawn or landscape.

Controlling yellow nutsedge can be difficult. Pulling the weeds is effective if you are willing to be persistent... especially if you start right away. I pulled the few plants I saw last week. You will kill new plants by pulling them before June 21. Young plants will not form tubers until day lengths start to shorten, after June 21, the longest day of the year.

However, if you pull a plant that is a year older or more, the small tubers it has already formed will sprout and it looks like the problem is as bad or worse than when you started. But don't give up... these new plants can be controlled if you pull them within a week after emergence because they haven't formed new tubers yet. However, if new plants are allowed to mature and develop tubers before being pulled, then hand pulling will not provide adequate control.

In areas of heavy yellow nutsedge infestation, chemical control may provide the only viable option. Common grass and broadleaf herbicides will not control yellow nutsedge. Specialized herbicides for controlling sedges must be used. The most effective herbicide currently available for yellow nutsedge control is Sedgehammer. Two or more application of herbicide will normally be needed to provide control. Success in controlling yellow nutsedge with a herbicide depends entirely on carefully reading and following label directions.

When applying herbicides to control nutsedge, avoid mowing three days before and one day after treatment. To ensure adequate herbicide absorption, do not water the lawn for at least 24 hours after product application. Applications should ideally be initiated in June when the nutsedge is young, actively growing, and is most sensitive to herbicidal control. Once this weed matures, control is difficult regardless of the treatment schedule.

For more information on yellow nutsedge control or other lawn weed problems, contact your local Nebraska Extension office.