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Perennial Ryegrass
Lolium perenne

Perennial ryegrass has become a popular component of lawn seed mixtures in the United States as a result of improvements in color, texture, and disease resistance. It is used widely because it establishes quickly and competes well. Ryegrass will germinate from seed in just two to four days and will provide a uniform lawn within two weeks.

Perennial ryegrass is a bunch-type grass that does not produce lateral growth in the form of rhizomes or stolons. Rather it spreads from the base by small shoots called tillers. This makes ryegrass plants less competitive in a lawn with regular traffic that injures the plant and leaves open spaces.

In high-traffic situations, Kentucky bluegrass is more competitive, producing rhizomes that can refill damaged spots. With ryegrass, weeds can often fill in open spaces before the grass can recover. While ryegrass tolerates abrasion better than Kentucky bluegrass, it does not recover adequately. Overseed regularly to maintain a competitive stand.

Perennial ryegrass is most successful in full sun with well-drained, fertile soil. It can tolerate mowing down to three quarters of an inch, but does best at 2 to 2.5 inches.

Ryegrass is not well-adapted to shade and drought conditions, and vigorous growth does result in thatch accumulation. Major disease problems include fungal diseases such as red thread, rust, brown patch, and Pythium blight. This is most likely a result of reduced growth from low fertility and environmental conditions conducive to fungal growth.

Ryegrass breeders have developed varieties that contain endophytic fungi. These beneficial fungi live in the leaf sheath and produce chemicals that deter surface feeding insects such as chinch bugs and sod webworm. Unfortunately, they have no effect on white grubs or other subsurface feeders.