When a lawn owner asks if grass spreads naturally, the answer depends entirely on the specific type of grass planted. The concept of “natural spreading” in turfgrass refers to vegetative growth, where a single grass plant physically expands across the ground to create a dense patch without the need for new seeds. This process, which creates a thick, uniform lawn, is determined by the internal biological structures that allow certain species to grow horizontally. Understanding these growth habits is the first step in managing a healthy, self-repairing turf.
The Biology of Lateral Turf Spread
The ability of some turf species to spread and form a continuous sod is due to specialized horizontal stems called runners. These runners are modified stems that allow the plant to colonize bare ground quickly and efficiently. The two main types of runners are classified by where they grow in relation to the soil surface.
The first type is the stolon, which is an above-ground runner that creeps along the soil surface. St. Augustinegrass and Bermuda grass are common examples of turf species that rely on stolons for their aggressive lateral expansion. New shoots and roots emerge from nodes along the stolon as the runner moves outward. This above-ground growth is visible and forms a dense, interwoven mat over time.
The second type of runner is the rhizome, a subterranean stem that grows horizontally beneath the soil surface. Kentucky bluegrass is a prime example of a grass that spreads robustly using rhizomes. The rhizomes push through the soil, sending up new grass shoots and roots at their nodes, which allows the turf to fill in bare spots from underneath. Some species, such as Zoysiagrass, utilize both stolons and rhizomes, making them effective at self-repair and forming thick turf.
Bunch Grasses: Growth Without Runners
In contrast to the spreading varieties, many popular turf species are known as bunch grasses because they lack the horizontal runners. These grasses, which include Tall Fescue and Perennial Ryegrass, expand only by a process called tillering. Tillering involves the growth of new shoots, or tillers, that emerge vertically from the crown of the original plant.
This growth habit results in a dense clump or bunch shape as the plant matures. Because the new growth stays tightly clustered around the mother plant, bunch grasses will not naturally spread across the lawn to fill in a damaged area. A bare patch in a fescue lawn will remain a bare patch unless new seed is introduced, often requiring regular overseeding to maintain a dense, uniform stand.
Encouraging Natural Grass Expansion
For turf owners with spreading grass varieties, maintenance practices can be adjusted to maximize their natural expansion capabilities. Mowing height is important, as cutting the grass too short stresses the plant and encourages vertical growth instead of lateral spread. Maintaining a higher mowing height, typically between two and three inches, promotes deeper root growth and conserves energy for producing runners.
Proper fertilization, particularly with nitrogen, is directly linked to the development of these runners. Nitrogen encourages vegetative growth, including the production and extension of stolons and rhizomes. Applying the correct amount of nitrogen during the grass’s peak growing season stimulates the plant to colonize available space.
Practices that improve soil conditions support the movement of the runners. Core aeration alleviates soil compaction, creating channels that allow rhizomes to penetrate the ground more easily and roots to grow deeper. Similarly, dethatching removes excessive layers of dead organic matter that can physically block above-ground stolons from making contact with the soil, allowing them to root and establish.