Turfgrasses that develop a dense, uniform stand rely on a specialized ability to spread horizontally across the soil surface. This lateral growth distinguishes turf-forming grasses from those that grow in isolated clumps, providing the foundation for a resilient and cohesive lawn. The spreading mechanism allows the grass to quickly fill in damaged or bare areas, creating a self-repairing quality desired in home lawns and athletic fields. Understanding how a grass propagates itself is important for selecting the right variety and determining necessary maintenance practices.
Understanding Spreading Mechanisms: Stolons and Rhizomes
The ability of a grass to spread is accomplished through two distinct types of modified stems: stolons and rhizomes. These structures function in vegetative reproduction, creating genetic clones of the parent plant. Both possess nodes, which are points of cellular activity from which new roots and shoots can emerge, establishing a new plant.
Stolons are above-ground stems that creep along the soil surface, sometimes called runners. These visible stems rapidly extend horizontally and periodically root down into the soil, allowing the turf to quickly colonize open ground. Because they operate on the surface, stolons provide rapid lateral coverage.
Rhizomes are modified stems that grow horizontally beneath the soil surface. These structures push through the soil, sending shoots upward to form new grass blades and roots downward to anchor the new plant. Because they are protected underground, rhizomes serve as an energy reserve, storing carbohydrates that help the grass survive periods of drought or cold weather.
Common Grasses That Utilize Stolons
Many warm-season turfgrasses rely heavily on stolons for aggressive spreading and recovery. St. Augustinegrass, popular in warm, humid regions, spreads exclusively by thick, robust stolons. This mechanism allows it to quickly form a dense, coarse-textured turf mat, but it also means the growing points are exposed to mechanical damage from heavy traffic or low mowing.
Centipede grass also utilizes stolons as its primary method of lateral expansion. This warm-season variety is known for its slower growth rate compared to other runners, resulting in a less aggressive spread. The stoloniferous nature of Centipede grass contributes to its characteristic low, dense growth habit, helping it maintain a uniform appearance in low-maintenance settings.
Bermuda grass and Zoysia grass employ both stolons and rhizomes. Bermuda grass stolons are particularly aggressive, allowing the plant to rapidly invade adjacent areas and quickly repair damage. Zoysia grass stolons spread more slowly than Bermuda, ultimately forming a very tough, wear-tolerant turf. The presence of these above-ground runners in both grasses is directly responsible for their tendency to develop thatch.
Common Grasses That Utilize Rhizomes
Grasses that rely on rhizomes often exhibit superior cold tolerance and resilience because their regenerative growing points are protected beneath the soil. Kentucky Bluegrass (KBG) is a premier cool-season turf that spreads almost entirely through rhizomes. This growth pattern allows KBG to form an exceptionally dense, sod-like matrix, making it highly tolerant of foot traffic and damage.
The rhizomes of Kentucky Bluegrass are responsible for its ability to quickly self-repair after injury. When turf is damaged, the underground stems grow into the bare area and sprout new plants, effectively knitting the turf back together. This deep, interconnected structure is a significant advantage in northern climates, where the protected stems can survive freezing temperatures.
The rhizomes of dual-spreading grasses, like Zoysia and Bermuda, provide an additional layer of protection and energy storage, enabling recovery from intensive use or heat stress. This is why Bermuda is frequently selected for high-traffic environments like golf courses and sports fields. Some varieties of Fine Fescue, such as Creeping Red Fescue, also utilize rhizomes, which contributes to their ability to spread and thrive in shaded or compacted soils.
Practical Impact of Spreading Habits on Lawn Management
The choice between a stoloniferous or rhizomatous grass profoundly impacts the practical demands of lawn management. Grasses that spread predominantly with stolons, such as St. Augustine, are generally easier to contain along borders and sidewalks because the runners are visible and can be trimmed with standard edging tools. However, these above-ground stems are more prone to forming a thick layer of thatch, which is a dense accumulation of dead and living organic material just above the soil line.
Thatch buildup requires regular maintenance, often involving vertical mowing or dethatching, to prevent the turf from thinning and becoming susceptible to disease. Conversely, grasses that rely heavily on rhizomes, like Kentucky Bluegrass, tend to produce less surface thatch but present a challenge for containment. Since the spreading stems are underground, they can easily travel beneath landscape edging and pop up unexpectedly in adjacent flower beds or walkways.
When a grass utilizes both mechanisms, such as Bermuda or Zoysia, the resulting aggressive growth leads to a highly durable turf with exceptional self-repair capability. This dual spreading ability allows the grass to withstand significant wear and tear, rapidly filling in divots and bare spots. Homeowners must be prepared for the corresponding need for frequent mowing and diligent use of landscape barriers to manage the plant’s vigorous lateral expansion.