Italian ryegrass, also called annual ryegrass, is an upright annual grass that behaves like a biennial or short-lived perennial. It grows vigorously in winter and early spring. Italian ryegrass and a related species, perennial ryegrass, Lolium perenne, are the two most common weedy ryegrasses in California. It is found throughout California to about 3300 feet (1000 m), except in deserts and the Great Basin and inhabits agricultural land and other disturbed places. Italian ryegrass and perennial ryegrass can hybridize, resulting in offspring that are difficult to identify as either species. Ryegrasses are cultivated for turf and forage. Sometimes Italian ryegrass is grown as a cover crop. Ryegrasses in the North Coast and other regions occasionally become infected with a fungus that causes an illness called “ryegrass staggers” in livestock.
Habitat
Roadsides, open fields, crop fields, pastures, orchards, and vineyards.
Seedling
Seedling leaves are shiny.
Mature Plant
Italian ryegrass grows erect to about 3 feet (0.9 m) tall. Stems grow singly or in clumps and are rounded to slightly flattened in cross-section. Leaf blades are flat, glossy, generally hairless, and range from 2-2/5 to 10 inches (6–25 cm) long. One characteristic distinguishing it from perennial ryegrass is that its leaves are rolled in the bud. Perennial ryegrass leaves are usually folded in the bud, but also can be rolled. Also leaf width can differ. Italian ryegrass leaves range from 1/10 to 2/5 of an inch (3–10 mm) wide; perennial ryegrass leaves range from 1/12 to 1/5 of an inch (2–5 mm).
Collar Region
Ligules are membranous and can grow to 1/10 of an inch (3 mm) in length. Auricles are usually well developed, up to 1/12 of an inch (2 mm) long, or are sometimes lacking.
Flowers
Flowering takes place from April through September. The flowerhead is 3 to 12 inches (8–30 cm) long. It consists of small, stalkless spikelets that are alternate to one another along the main flowering stem. Occasionally they branch off the main axis. Italian ryegrass has long needlike awns on the individual flowers (florets), and more florets are clustered per spikelet than in perennial ryegrass.
Reproduction
Reproduces by seed.
Related or Similar Plants
- Perennial ryegrass, Lolium perenne
