Italian ryegrass, Lolium multiflorum, is a winter annual that is widely used as as a cover crop. Annual ryegrass does well on heavy, waterlogged soils; its extensive system of roots and vigorous growth makes it useful as a nurse crop for fall legumes and as a catch crop for excessive nitrogen.
The glossy leaves of annual ryegrass grow up to 12 inches tall and are yellowish-green at the base. It is a bunching grass, meaning that it grows in tufts or clumps rather than forming a mat or sod.
Annual ryegrass is a cold-tolerant grass that will germinate in cooler temperatures than most cover crop grasses. In the northeastern U.S., it tends to be biennial, growing vigorously until dormant in the winter then growing quickly in the spring, producing seed by mid-June. On the Pacific Coast, it is a winter-growing annual.
Researchers at Mississippi State University say annual ryegrass does best at soil pH levels between 6 and 7 but will tolerate a wide pH range. It likes silty or heavier clay soils with good drainage although it will grow on well-fertilized, sandy soils. Annual ryegrass grows vigorously and can be used as a cover crop on cropland subject to temporary flooding and on grass waterways, flood canals and places where water pools. It does best with at least 12 inches of annual rainfall.
Horticulturists at the University of California at Davis say annual ryegrass can assimilate up to 200 pounds of nitrogen per acre each year. Use 100 pounds of nitrogen and 50 pounds of phosphoric acid per acre to prepare beds for seeding lawns. For heavy production of pasture or hay, apply 75 to 100 pounds of nitrogen per acre each fall. If annual ryegrass is grown with a legume, additional phosphorus and potassium need to be added.
Sow seeds in the fall on the Pacific Coast and southeastern states. In the Northeast, sow seeds in the early spring, late summer or fall 40 days before the usual date of first frost. The College of Agriculture and Life Sciences at Cornell University recommends drilling seed at 10 to 20 pounds per acre; if the seed is broadcast, cover with 1/2 inch of soil.
Maintenance and Mowing
If it's permitted to drop seed, annual ryegrass can persist almost indefinitely. If it's used for a temporary cover, mow it and then disk or plow it under during early bloom. Mow temporary lawns no closer than 3 inches. For high-quality hay, cut it no later than early bloom.
Use of Herbicides
The spread of annual ryegrass can be controlled using weed oil or non-persistent contact herbicides including those containing glyphosate. In places where ryegrass is considered a weed, chlorsulfuron can be used to prevent its seeds from germinating.