After the snow melts and everybody gets antsy for spring to arrive, we start to notice the not-so-green parts of the lawn. One of the most abundant and troublesome grassy weeds out there is nimblewill. The circular straw-colored patches of dormant nimblewill are very noticeable from early fall to late spring. The patches start small and round, but can eventually spread over most of the lawn area.
Nimblewill goes dormant in early fall when the day lengths shorten and temperatures drop. And green up occurs much later than our cool season turf.
Nimblewill spreads by seeds and by stolons. The seedheads are formed from mid-summer on. They are a slender spike. The stolons are very thin and wiry with small, rounded, bead-like nodes. Roots form at the nodes. The stolons create a spreading patch that can grow 1-2 feet in diameter each year. When mowed it forms dense round patches. When unmowed, it grows upright and rangy to a height of 18-24 inches.
Stolons close-up showing thin, wiry stem and round nodes, with roots and new shoots growing from the nodes.
Nimblewill has a fibrous root system and can be easily pulled from the ground. This is deceiving to people who think it is easily removed by pulling. Any small piece left in the ground will start new growth.
Fibrous root system and a tangle of stolons
The leaves are short (about 1-2 inches long) and 1/4 inch wide, flat, blue-green, with many veins visible on the upper surface. They are often held at a 45 degree angle to the stem. The leaves are rolled in the bud. There is a very short, membranous ligule with a somewhat jagged top.
Leaves of Nimblewill
Nimblewill can be confused with either creeping bentgrass or bermudagrass. Some quick ways to tell them apart: Bentgrass is a cool season grower, so it maintains green color into fall past frost. Bermudagrass has stolons and rhizomes that are flatter and much thicker; and seedheads with 3-7 finger-like spikes arranged like a pinwheel.
It is not easy to out-compete nimblewill by overseeding cool season grasses into it. Mechanical spread of nimblewill can occur when stolons are cut and pieces are spread during aeration or thatching operations. Mechanical removal by raking or digging is possible, but success depends on complete removal of the stolons and pieces. Patches or large areas can be treated with glyphosate when actively growing, then re-seeded or sodded.
Nimblewill in turf
There is now a post-emergent, systemic, selective herbicide to use against nimblewill. Tenacity is newly labeled for home lawn use. Mesotrione, the active ingredient in the herbicide Tenacity, is extremely effective and can be used to selectively remove nimblewill from cool season turfgrasses. It is best applied as a spot treatment on residential lawns, and repeat treatments 2-3 weeks apart are necessary (maximum of three treatments). Tenacity will turn nimblewill white. It will turn turfgrasses white also - the white discoloration appears about a week after treatment and can last for several weeks. For complete information, read the label.
White leaves of nimblewill following Tenacity treatment
North Carolina State University Turffiles.
Purdue University Perennial Grasses.
University of Nebraska-Lincoln. Weed Control- Nimblewill.
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