Ryegrass, whether annual or perennial, is a cool-season turf that establishes quickly and provides a bright green color. Ryegrass does not spread in the way many other popular lawn grasses do. It is fundamentally a bunch grass, meaning its individual plants grow vertically in clumps rather than horizontally across the soil. This growth habit dictates how a ryegrass lawn must be maintained to achieve a thick, uniform turf.
Understanding Bunch Grass Growth
The growth pattern of ryegrass is defined by tillering, which involves the production of new shoots, or tillers, that emerge from the base of the parent plant. These new shoots grow upward, remaining attached to the original plant crown, resulting in a dense cluster or bunch. This mechanism explains why ryegrass cannot fill in bare patches on its own and why individual plants appear clumpy if not planted densely.
This mechanism contrasts with spreading grasses, which use specialized lateral stems to colonize new ground. Creeping grasses, such as Kentucky Bluegrass or Bermuda Grass, spread either through above-ground stems called stolons or below-ground runners known as rhizomes. Stolons root at nodes along the soil surface to form new plants, while rhizomes perform the same function entirely beneath the soil.
Since ryegrass lacks both stolons and rhizomes, its expansion is limited to the slight widening of the original bunch as new tillers emerge adjacent to the primary shoot. The individual plants remain distinct, and the grass cannot produce the dense, interwoven sod layer that characterizes spreading grasses. This inability to spread laterally means that any damage or thin area must be corrected by introducing new seeds, as existing plants will not grow over the spot.
Annual Ryegrass Versus Perennial Ryegrass
Confusion about whether ryegrass spreads often stems from the different life cycles of its two main types: annual ryegrass (Lolium multiflorum) and perennial ryegrass (Lolium perenne). Annual ryegrass is a short-lived grass that completes its life cycle in a single growing season, often used for temporary winter color or erosion control. It dies off when summer temperatures rise, necessitating reseeding if temporary cover is desired the following year.
Annual ryegrass is a prolific seed producer, dropping abundant seeds that germinate aggressively the following season, leading to the perception that it spreads rapidly. This aggressive self-seeding allows it to colonize large areas quickly, often making it appear like a weed in established perennial lawns. Its ability to germinate and establish within five to seven days contributes to its reputation for “taking over” an area.
Perennial ryegrass has a longer life span, persisting for multiple seasons in appropriate climates, making it suitable for permanent turf. It is finer in texture and darker green than the annual variety and is frequently included in cool-season grass seed mixes. While it produces seed, it is less aggressive in its seeding habits than annual ryegrass. Its persistence is due to its multi-year life cycle rather than prolific self-seeding.
How Ryegrass Achieves Density
Because ryegrass is a bunch grass that cannot spread laterally to fill in gaps, achieving a thick, uniform turf requires specific cultural practices centered on maximizing tillering and introducing new seeds. Establishing a dense stand requires correct initial seeding rates and consistent overseeding. A high number of plants per square unit is necessary from the start since the individual plants will not connect via runners.
To encourage existing ryegrass to thicken, proper fertilization and mowing heights promote heavy tillering. New tillers are produced year-round, with peak production often occurring in the late spring. Maintaining the correct leaf-canopy height encourages the development of these new shoots. For turf purposes, maintaining a mowing height between one and two inches promotes the proliferation of tillers, which increases the shoot density and helps the lawn appear more uniform.
Managing the aggressive self-seeding of annual ryegrass is necessary to prevent it from becoming a dominant component of a mixed lawn. Homeowners can manage this by timing mowing to prevent the formation and maturity of seed heads. Alternatively, applying pre-emergent herbicides before the seeds germinate in the spring stops the annual cycle, preventing the temporary grass from returning in abundance the following season. These management practices are essential to maintaining the desired density and composition of a ryegrass lawn.