A patchy lawn is a common frustration for homeowners. Whether your grass will naturally fill in depends entirely on the specific growth habit of the turfgrass species you have. Understanding this biological trait is the first step toward achieving a dense, uniform lawn. The process relies on the presence or absence of specialized horizontal stems that dictate how a plant expands its territory.
How Grass Types Determine Natural Spread
Turfgrasses fall into two primary categories based on how they propagate and spread across the ground. The most effective self-repairing grasses rely on horizontal, modified stems known as runners, which allow the plant to colonize open soil aggressively.
Some grasses, such as Kentucky Bluegrass, use underground runners called rhizomes. These subterranean stems grow horizontally beneath the soil surface, establishing a new plant away from the parent. Other spreading grasses, like St. Augustine and Centipede grass, produce above-ground runners called stolons that creep along the soil surface, rooting down at nodes. Warm-season grasses like Bermuda and Zoysia are particularly effective self-repairers because they produce both rhizomes and stolons, enabling them to fill in large damaged areas quickly.
The second category is bunch-type grasses, which lack these horizontal spreading stems. These grasses, including Tall Fescue and Perennial Ryegrass, grow in dense, isolated clumps that expand only by producing new vertical shoots called tillers from the crown. Since they do not creep laterally, a bare spot will remain until it is physically filled in through overseeding or patching.
Identifying Your Lawn’s Growth Habit
Determining your lawn’s growth habit requires a simple visual inspection of the grass plant itself. If your grass is a spreader, you will be able to see or feel the modified stems running away from the main cluster of grass blades. For stoloniferous grasses, look closely at the edges of your lawn, where you may find thick, straw-like stems creeping over sidewalks or into adjacent flower beds.
Identifying rhizomes requires a more hands-on approach, as they are not visible above ground. Gently dig up a small section of turf near a thin or bare area to look for the distinctive white or pale-colored stems running horizontally just below the soil surface. If you see distinct, isolated tufts of grass that never merge with their neighbors, you likely have a bunch-type grass.
Maximizing the Fill-In Potential
If you have identified a spreading turfgrass, you can encourage its natural ability to fill in gaps through specific maintenance practices. Mowing at the proper height is important, as cutting too low forces the plant to prioritize vertical growth over the lateral energy needed to produce runners. For most warm-season spreaders like Bermuda and Zoysia, maintaining a height between 1.25 and 2.5 inches encourages a dense, lateral spread.
Providing the right nutrients, particularly nitrogen, directly fuels the development of new rhizomes and stolons. Instead of a single heavy feeding, applying smaller amounts of nitrogen (approximately 0.5 pounds per 1,000 square feet) more frequently supports continuous runner production. Potassium (K) also improves the vigor and establishment of these lateral stems, aiding in overall recovery.
Ensuring the soil environment is conducive to underground stem growth will maximize the fill-in process. Core aeration helps alleviate soil compaction, making it easier for rhizomes to bore through the earth and establish new plants. Consistent, deep watering encourages the establishment of newly rooted nodes, allowing the spreading grass to successfully colonize the open areas.