In California, Italian ryegrass germinates with the onset of the fall rainy season , generally when temperatures dip below 50 degrees Fahrenheit (10 deg C) . Growth is initially rapid, slows in the winter, then increases again in the spring [7,24]. Spring growth does not occur until the mean daily temperature rises above 50 degrees Fahrenheit (10 deg C) for several days, usually in late February in southern California. No growth occurs until March above 2,500 feet (760 m) .
Although aboveground growth slows in the winter, Italian ryegrass roots continue to grow. In mid-January in California, roots averaged 8 inches (20 cm) deep, and in early March roots averaged 12 inches (30 cm) deep while seedlings were still in the two- to three-tiller stage. By mid-April, roots were 23 inches (58 cm) deep and most tillers had been produced. Italian ryegrass roots excavated in July were 56 inches (142 cm) deep .
Italian ryegrass begins drying in late April in California . In 1960 near Berkeley, maximum Italian ryegrass biomass occurred in late May .
In Colorado, anthesis begins in June and ends in July. In Montana, it begins in May and ends in July .
Italian ryegrass is a quick, effective groundcover for erosion control and as a winter cover crop . It is often used for temporary erosion control; it does not generally persist in cold ecosystems such as in Alaska, nor does it tend to spread into adjacent undisturbed areas . It has a lower pH limit of 4.5. Seeding rates are described .
Seeding of Italian ryegrass is often followed by seeding with perennial species the following year. If seeded together, Italian ryegrass often outcompetes the perennials [25,63].
Although Italian ryegrass is one of the most commonly used grasses for revegetating burned sites, its use is controversial. Discussion of this controversy is in FIRE MANAGEMENT.
A fine, firm seedbed gives the best results. Mulched seedings on graded soil germinate readily. Spring seedings of ryegrass may occur in March, April, or May. Seeding rates will vary with local conditions and purpose of plantings. Generally, a seeding rate of 20 to 25 pounds per acre is used if ryegrass is seeded alone. Lesser amounts per acre are used in mixtures, depending upon uses and companion species. Do not exceed 4 pounds per acre in mixes with alfalfa.