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Weed Identification




Scientific Name

Agrostis gigantea

Synonyms (former Scientific Names):

Agrostis stolonifera ssp. gigantea
Agrostis nigra
Agrostis stolonifera var. major
Agrostis alba


A perennial grass that forms large mats or swards. It grows upright reaching 2 to 3 feet in height.


Leaves are narrow and sharp with a bluish to grayish green color. Leaf blades can be 5 to 8 inches long and 8 mm wide. The leaves and sheaths are also hairless. The leaf has a tall membranous ligule (3 to 6 mm).

Identifying Characteristics

Redtop is a rhizomatous perennial grass that makes a coarse but fairly dense turf. Because of its tiny seed, redtop should have a firm, well-prepared seedbed. It may be sown in early spring or late summer. Seeding depth is 1/4 inch. Redtop is seldom seeded alone, except for temporary cover. Rates of seeding will vary depending upon purpose, and whether seeded alone or in mixtures. In mixtures, rates of 1 to 2 pounds per acre are generally used. For pure stands, seeding rates are from 4 to 5 pounds per acre. The higher rates are used for temporary critical area stabilization. Redtop grows rapidly after seeding and excessive seeding rates are not recommended, particularly in mixtures. When used for erosion control on critical areas, fertilizing is essential to give rapid cover.

Flower Seed Head

The inflorescence is pyramidal and reddish in color--hence the common name of redtop. There are approximately 4,990,000 seeds per pound.

Seed Fruit

Seed grain reddish in color and elliptical shaped. They are 1 to 1.2 mm long

Where Found

Redtop is widespread in the Northeast. It has better growth in the humid North than in the warmer climates of the Southern portions. Redtop was introduced throughout most of the United States and Canada. It prefers fields, pastures and roadsides. Grows better during the cool months and struggles during hot summer months.

Leaf Hair on Upper Surface

no hairs

Leaf Arrangement

rolled in bud

Mature Leaf Width

less than 5 mm
6 to 15 mm





Life Cycle



not present



Ligule Length

2-3 mm
more than 3 mm

Plant Type