Ryegrasses  (Lolium spp. Italian ryegrass (Lolium multiflorum) Perennial ryegrass (Lolium perenne))

The most common weedy ryegrasses in California are Italian ryegrass, Lolium multiflorum, also called annual ryegrass, and perennial ryegrass, L. perenne. Italian ryegrass is a winter annual or biennial grass that sometimes behaves as a short-lived perennial. Perennial ryegrass, on the other hand, is a short-lived perennial that behaves like an annual or biennial under poor conditions. Both grasses are found throughout California to about 3300 feet (1000 m), except in deserts and the Great Basin. Ryegrasses inhabit agricultural land and other disturbed areas. They can hybridize with one another, 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

Both Italian and Perennial ryegrasses grow 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 distinguishing characteristic between the two is that Italian ryegrass leaves are rolled in the bud whereas perennial ryegrass leaves are usually folded in the bud (but also can be rolled). Another difference is that the leaves of Italian ryegrass range from 1/10 to 2/5 of an inch (3–10 mm) wide and those of perennial ryegrass range from 1/12 to 1/5 of an inch (2–5 mm) wide.

Collar region

Ligules are membranous and up 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, spikelets that are spaced apart along the main flowering stem and are alternate to one another. Occasionally spikelets branch off the main axis. Italian ryegrass has longer needlike awns on the individual flowers and more flowers are clustered per spikelet than in perennial ryegrass.

Reproduction

Reproduces by seed.

Related or similar plants

• Italian ryegrass, Lolium multiflorum

More information

• Grass ID illustration
• Italian ryegrass, Lolium multiflorum Calflora's distribution map
• Perennial ryegrass, Lolium perenne Calflora's distribution map
• For agriculture: UC IPM Pest Management Guidelines