A tiller in grass is a new shoot or lateral stem that grows from the base of the main grass plant. This process of new shoot production, known as tillering, is fundamental to how grasses establish, survive, and form dense turf. Tillers develop from buds near the soil surface and initially rely on the parent plant for resources until they develop their own leaves and root system. The presence of numerous tillers is a defining feature of a healthy lawn, creating the thick, carpet-like appearance turf is known for.
Anatomy and Formation of a Grass Tiller
Tillers originate from small, undeveloped growing points called axillary buds, located at the nodes near the base of the main stem. These nodes and buds are tightly clustered in the central, compact structure at the soil line, known as the crown. The activation of these axillary buds initiates the tillering process, allowing the grass plant to produce a new, independent shoot.
As the bud begins to grow, the new shoot emerges, consisting of successive segments called phytomers (including a leaf sheath, a leaf blade, and a growing point). The new tiller remains connected to the parent plant, sharing the root system and vascular tissue until it matures and develops its own adventitious roots from its lower nodes. Tillers that grow straight up within the leaf sheath are common in bunch-type grasses, such as fescues, resulting in a clumping growth habit.
In other grass types, the new shoot may briefly grow sideways before turning upward, which is often associated with the development of modified horizontal stems. Whether the new shoot grows primarily vertically or slightly outward, the result is a functional stem capable of photosynthesis and contributing to the overall plant size. The plant’s energy status, specifically the stored carbohydrates in the crown, significantly influences the rate at which new tillers are produced.
How Tillering Affects Turf Density
Tillering is the primary way grass increases its shoot density, resulting in a thicker, more robust lawn. The production of new shoots allows the grass to fill in open spaces, creating a tight canopy that resists weeds and better withstands foot traffic. This shoot multiplication is often stimulated by routine maintenance practices, particularly mowing.
When the grass is mowed, the removal of the upper leaf tissue also removes the apical meristem, which is responsible for upward growth. This defoliation alters the plant’s hormonal balance by reducing hormones that suppress lateral bud growth. The release of this suppression encourages the axillary buds at the base of the plant to activate and grow into new tillers.
Regular mowing, therefore, promotes the development of numerous, shorter shoots, which is a desirable response for creating dense turf. This increased shoot density is a form of vegetative reproduction, allowing the grass to maintain and increase its ground cover without relying on seed production. The plant adjusts to consistent leaf tissue removal by concentrating growth energy into producing these lateral shoots, resulting in a denser stand of grass.
Distinguishing Tillers from Stolons and Rhizomes
Tillers, stolons, and rhizomes are all lateral stems that contribute to a grass plant’s spread, but they differ significantly in their direction of growth. A tiller is primarily a vertical shoot that grows upward from a bud at the base of the main plant, resulting in a vertical thickening of the grass clump. It remains attached to the parent stem, leading to a bunch-type growth habit if tillers are the only form of lateral spread.
In contrast, stolons and rhizomes are specialized horizontal stems that are the primary means of lateral colonization for many turfgrass species. Stolons, sometimes called runners, are modified stems that creep along the soil surface. These above-ground stems have nodes that root down into the soil, establishing new plants along their length.
Rhizomes are similar to stolons but grow horizontally beneath the soil surface. These underground stems also have nodes that initiate new roots and shoots, allowing the grass plant to spread aggressively and form a dense sod. While tillers thicken the plant vertically, stoloniferous and rhizomatous grasses use their specialized stems to spread horizontally, which is why they are described as creeping grasses.