Weeds Identification Gallery

Annual Bluegrass

  • Poa annua
  • Grass Family: Poaceae
Updated: 09/2025

Annual bluegrass is a short, cool-season annual, biennial, or perennial grass. It is highly variable and is one of the most common weeds found throughout California, especially in coastal regions up to an elevation of 6600 feet (2000 m). Habitats include agricultural land and other disturbed areas. It can easily be distinguished from other grasses by its leaf tip, which is shaped like the bow of a boat.

Habitat

Turf, gardens, landscape areas, fields, roadsides, vegetable crops, vineyards and orchards.

Seedling showing broad, blunt leaf blades with tips turned up like a boat's prow; . Credit: Jack Kelly Clark, UC IPM
Seedling. Credit: Jack Kelly Clark, UC IPM

Collar Region

The membranous ligule is rounded with a slightly pointed, jagged tip.

A collar region where a blade angles away from the main stalk. A second blade juts to the right from the main stalk below. Copyright information is at the bottom (Copyright 2007 The Regents of the University of California. All rights reserved.). Credit: Joseph M. DiTomaso, UC Agriculture and Natural Resources
Collar region. Credit: Joseph M. DiTomaso, UC Agriculture and Natural Resources

Mature Plant

Annual bluegrass growth is characterized by the spreading of dense, low clumps, 3 to 12 inches (8–30 cm) tall. Leaf blades are hairless, often yellowish green, and sometimes dark green. They are often crinkled at the midsection. It often roots at lower stem nodes and the root system is fibrous.

Mature plant showing bright green color and flowering heads, . Credit: Jack Kelly Clark, UC IPM
Mature plant. Credit: Jack Kelly Clark, UC IPM

Flowers

Visible mostly December through July, although in some sites it can be found nearly year round, the annual bluegrass flower head is triangular to egg shaped in outline. It branches more than once, is often pale, and at times, bright green to purplish. It has about three to eight flowers per spikelet.

Spikelet and leaf blades showing bright green color and yellow flowers; . Credit: Jack Kelly Clark, UC IPM
Flower cluster. Credit: Jack Kelly Clark, UC IPM

Reproduction

Annual bluegrass reproduces by seed and can have many generations in a season.

Leaf blade showing tip curved like a boat's prow, 2X; . Credit: Jack Kelly Clark, UC IPM
Leaf tip. Credit: Jack Kelly Clark, UC IPM

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