Well adapted to areas that experience heavy foot traffic, perennial ryegrass (Lolium perrene) is a vigorously growing, clump-forming type of grass. When starting or reseeding a lawn of pure perennial ryegrass, increase the standard seeding rate by 10 to 20 percent to quickly fill in the area. However, perennial ryegrass will often out-compete other varieties of grass in seed mixtures due to its fast-germinating and rapidly establishing qualities.
Winter Die Back
Although it is considered a cool-season grass, perennial ryegrass can suffer die back during severely cold winters that have little or no snowcover. To keep a thick and dense lawn, a maintenance program that includes overseeding in spring will help mitigate winter die back.
A pure stand of perennial ryegrass will be difficult to mow cleanly. This is due to its tough, fibrous blades. Use of a freshly-sharpened lawn mower will help alleviate this.
Intolerant of Shade
Perennial ryegrass is intolerant of shade and grows best in full sun situations. Under optimal growing conditions, it is fast-germinating and quick to become established, often out-competing other types of grass in seed mixtures.
Keeping to a consistent maintenance scheduled will ensure that your stand of perennial ryegrass looks its best. Provide it with adequate moisture---at least one inch per week---and mow regularly to keep the blades about 2-inches long in summer and slightly shorter during cooler spring and fall weather. Improperly maintained pure stands of perennial ryegrass becomes bunchy, loose quality and develops bare spots.