Controlling Nutsedge in Turfgrass

Controlling Nutsedge (Nutgrass) in Lawns

Brian Jervis: Ask A Master Gardener

Tuesday, June 13, 2017

Q: What is the best way to control nutgrass? I have several patches of it which are spreading. Stewart, Tulsa.

A: Nutgrass, or more correctly, nutsedge, is one of the most difficult weeds to control, both in the lawn and agriculturally. Because it is a sedge, not a grass or a broadleaf weed, its biological system is such that it does not respond to the herbicides commonly used for other weeds.

There are two types of nutsedge — yellow and purple. We primarily have the yellow variety. This plant can be recognized by its slim grass-like leaves and stems, which are triangular (basis of the adage “sedges have edges”). It also grows more rapidly than most turfgrasses and usually pops up in a lawn 2-3 days after mowing. This weed thrives in hot, full sun and moist soils. Because of the preference for wet soils, our record rains this spring will likely yield a bumper crop.

The weed’s ability to reproduce makes it difficult to control. Although it can spread by underground rhizomes and seeds, the main type of reproduction, and the one that gives it the name “nutsedge,” is the ability to produce a large number of nutlets — hundreds per plant in one growing season. Each nutlet can produce a new plant, and the nutlets may lie dormant for years before sprouting as growing conditions become favorable. This also is the reason that pulling the weed out by hand is frustrating — the nutlets remain and the weed returns.

Nutsedge is introduced into lawns from seeds but more commonly from using mulch or fill soil that is contaminated with the nutlets. It also may enter a lawn or flower bed by contaminated nursery stock.

Control of nutsedge should first begin with prevention. The single most effective preventative measure for all weeds is to have a thick healthy and mowed tall lawn that will compete with all weeds. Also, watering lawns only when needed will prevent overly moist soils in which nutsedge thrives. Another preventative measure is to be selective in all soil imported to your lawn for fill or from nursery stock.

Once nutsedge is established, the best approach to control is the use of an herbicide. Pulling up the nutsedge plants after they have formed nutlets is frustratingly ineffective.

The chemicals recommended for nutsedge, for the most part, cover other sedges. Several herbicides are available to homeowners that are labeled for nutsedge control. They are found in many brands, with the chemicals bentazon, imazaquin, sulfentrazone or halosulfuron being at the top of the list. Of these options, sulfentrazone and halosurfuron are preferred. Both of these are tolerated by our commonly used grasses. Because of the waxy coat of nutsedge, some will need a “spreader sticker” added to the herbicide. This helps the chemical to adhere to the plant’s leaves. Be aware that they will need to be applied twice in a summer, and it may take 2-3 years for complete control.

Garden tips

·        Renovate overgrown strawberry beds after the last harvest. Start by setting your lawnmower on its highest setting and mow off the foliage. Next, thin crowns 12 to 24 inches apart. Apply recommended fertilizer, pre-emergent herbicide if needed and keep watered.

·        White grubs will soon emerge as adult beetles. This group of beetles’ color may vary from green to brown and vary from ¼- to ½-inch long. Watch for high populations that can indicate potential damage from their grubs later in the summer after egg laying.

·        Continue to fertilize warm-season grasses at 1 pound nitrogen per 1,000 square feet. Don’t fertilize fescue and other cool-season grasses during the summer. Because nitrogen is soluble in water, much of it may have been lost due to percolation and runoff, if you fertilized before recent rain