Bentgrass is a fine-textured, cool-season perennial turfgrass known for creating exceptionally dense, smooth surfaces. Belonging to the genus Agrostis, it is highly valued in specific applications for its unique growth habit. Bentgrass is a defining feature of high-end turf, but its demanding nature requires precise, specialized management practices, often causing frustration in a typical lawn setting.
Defining Bentgrass and Where It Thrives
Bentgrass is a member of the grass family Poaceae, with the genus Agrostis encompassing approximately 150 species globally. It thrives in temperate regions of the Northern Hemisphere, particularly in cool, moist, and humid environments. Many species were historically native to wet areas, which explains their affinity for consistent soil moisture.
The primary commercial use of bentgrass, especially Creeping Bentgrass (Agrostis stolonifera), is in high-quality athletic fields. Its fine-bladed structure and tolerance for extremely low mowing heights make it the preferred choice for golf course putting greens and tees. This dense turf provides the smooth, consistent surface necessary for ball roll precision. The grass spreads aggressively via above-ground stems called stolons, forming a solid, uniform turf layer.
Key Characteristics of Common Varieties
Creeping Bentgrass (Agrostis stolonifera) is the most aggressive variety, recognized by its vigorous, above-ground runners (stolons). This growth habit allows it to form a dense mat that tolerates cutting heights as low as 0.25 inches or less. Its strong recuperative ability, due to the extensive stolon system, helps it recover quickly from damage.
Colonial Bentgrass (Agrostis capillaris) is less aggressive than the creeping type, spreading primarily by short underground stems (rhizomes) and tillers. It forms a less dense, more upright turf, making it less tolerant of ultra-low mowing heights. This variety is sometimes used for fairways or home lawns in cool, humid climates because it requires less intensive management and has better drought tolerance than Creeping Bentgrass.
Velvet Bentgrass (Agrostis canina) features the finest leaf texture of all bentgrasses, lending a distinctive, velvety appearance. While it tolerates close mowing, its spread by stolons is much weaker than Creeping Bentgrass, causing it to grow almost like a tufted grass at green heights. This variety is notable for its shade tolerance and lower requirements for fertilizer and irrigation compared to Creeping Bentgrass.
Specialized Maintenance Needs
Maintaining bentgrass, especially for putting green quality, requires a specialized and intensive cultural program. Mowing must be frequent, often three to four times per week during the growing season, using a reel mower to achieve extremely low heights (0.25 to 0.75 inches). This low cut encourages the lateral spread and density that gives bentgrass its desirable texture.
The irrigation needs of bentgrass are unique due to its shallow root system and dense growth. Instead of deep, infrequent watering, it often requires light, frequent watering to keep the upper soil moist and manage the dense thatch layer that is prone to drying out. During periods of high heat, a light misting, known as syringing, may be necessary to cool the turf and prevent heat stress.
Fertilization focuses on consistent, light applications of nitrogen rather than heavy, infrequent feeding. This schedule promotes steady, healthy growth without causing excessive flushes that can lead to disease or thatch buildup. Regular applications of a balanced fertilizer formulated for cool-season grasses are applied in the early spring and late summer to early autumn.
Regular cultivation practices are necessary to manage the significant thatch layer that bentgrass naturally produces. Core aeration is performed one or more times annually to alleviate soil compaction and improve the movement of air, water, and nutrients into the root zone. Topdressing with sand is also a routine practice, used to dilute and manage the accumulating thatch, creating a smoother and firmer playing surface.
Strategies for Control in Mixed Turf
When bentgrass appears as an unwanted grass in a standard cool-season lawn of Kentucky bluegrass or fescue, control becomes necessary. Cultural practices that favor desirable turfgrasses can be adjusted to discourage bentgrass patches. Raising the mowing height to around three inches shades the low-growing stolons, making it difficult for them to spread and compete.
Altering the watering schedule is an effective cultural control method. Since bentgrass has shallow roots and thrives in constant moisture, changing to deep and infrequent irrigation encourages the deeper root growth of desirable grasses and stresses the bentgrass. Reducing excessive or poorly timed nitrogen fertilization can also help suppress the bentgrass, which aggressively uses these nutrients.
For direct removal, homeowners have two primary chemical approaches. Small, isolated patches can be spot-treated with a non-selective herbicide, which kills all vegetation it contacts, requiring reseeding or resodding of the treated area. The treatment should extend approximately six inches beyond the visible patch to ensure the elimination of hidden stolons.
A selective control option for larger areas uses specialty herbicides containing the active ingredient mesotrione. This chemical targets the bentgrass without severely damaging surrounding cool-season turfgrasses like Kentucky bluegrass or fescue. This approach involves a series of two to three applications spaced about two weeks apart during the warmer months when the grass is actively growing.