Cool Season Grass Weeds

September 20, 2018
  • Poa Annua Weed Cool Season

Cool Season Grass Weeds

In the previous blog, Types of Turfgrass Weeds, we told you that grasses have leaves with veins that turn parallel to each other and are two-ranked. We also classify these grass weeds by season; cool season and warm season. Here we share with you examples of cool season grass weeds and how to tell which weed you may have in your lawn.

 

Annual Bluegrass (Poa annua)

Other names: Poa, Wintergrass

Life Span: Cool season winter annual (subspecies exist which act as short-lived perennials)

Poa Annua PlantDescription: Annual bluegrass is a light green bunch type grass. The leaf blades are soft, “V”-shaped, folded in the bug, and boat-shaped at the tip. The ligule is long pointed, and membranous. Auricles are absent. The root system is fibrous and does not have rhizomes. Annual bluegrass grows low and is capable of producing seed heads at mowing heights lower than ¼ inch. Growth from seed starts in early fall and often continues through the winter. This grass thrives in cool, moist conditions and may die suddenly during hot weather.

Rough Bluegrass (Poa trivialis)

Other names: Roughstalked Bluegrass, Rough Meadowgrass, Birdgrass

Life Span: Cool season perennial

Rough BluegrassDescription: Rough bluegrass is a light green to yellow-green stoloniferous grass. The leaf blades are soft, “V”-shaped, folded in the bud, and boat shaped at the tip. The ligule is membranous, long, pointed, and toothed near the tip. Auricles are absent. Collar is broad, smooth, and divided. Sheath is compressed, rough to the touch, and can be green or purple. The root system is fibrous. Rough bluegrass has become a weed problem in Kentucky blue-grass turfs due to seed contamination. In cool, wet springs rough bluegrass stolons from a single plant can spread 2-3 feet, giving the turf a patchy appearance. Rough bluegrass thrives in cool, moist conditions but often will go dormant and turn brown in summer.

 

Tall Fescue (Festuca arundinacea)

Other names: None

Life Span: Cool season perennial

Thick Blade FescueDescription: Tall fescue is a relatively coarse, bunch-type grass. The leaf blades are rolled in the bud, strongly veined on the upper surface, and rough along the edges. The ligule is membranous and short. Auricles are rudimentary. The lower portion of the stem is reddish purple, particularly in the spring and fall. The root system is manly fibrous with rudimentary rhizomes. The seed head is an erect, somewhat compressed panicle. Tall fescue clumps are objectionable in fine textured turfs. Tall fescue has good heat and drought tolerance which allows this grass to invade drought stressed turfs. This coarse grass results in brown fibers on the leaf tips, especially if the mower is dull.

 

Smooth Brome (Bromus inermis)

Other Names: None

Life Span: Cool season perennial

Brome GrassDescription: The leaf blades are rolled in the bud, about ¼ – to ½- inch wide, tend to be lax, and often form a constriction which appears and an “M” or “W”. The ligule is membranous and short. Auricles are absent. The lower portion of the stem is white with prominent veins. The root system is strongly rhizomatous. The seed head is an erect panicle, with branches in a circular pattern around the main stem. Smooth brome infestations usually result from lawns being started from pasture sod. Smooth brome starts growth early in the spring, slows during summer and resumes growth in the fall.

 

Quackgrass (Agropyron repens)

Other Names: None

Life Span: Cool season perennial

QuackgrassDescription: The leaf blades are rolled in the bud, flat, about ¼ inch wide, lax, and rough on the upper surface. The ligule is membranous and short. Auricles are conspicuous, claw-like, and clasp around the stem. The lower portion of the sheath has short hairs. The stem is erect and branched at the crown. The root system is strongly rhizominous, being yellow or white and very extensive. Rings of fibrous root hairs occur every3/4 to 1 inch along the rhizomes. The seed head is an erect spike, 2 to 5 inched long. It is not very heat tolerant and grows most vigorously during the early spring and fall.

 

Reference

R.E. Gaussoin and A. R. Martin. (1997). Turfgrass Weed Identification and Prevention. In F. Baxendale, Ph.D., & R. Gaussoin, Ph.D., Integrated Turfgrass Management for the Northern Great Plains (pp. 84 – 96). Location: Nebraska

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