Bermudagrass (as a weed)

Bermudagrass is a low, aggressively creeping warm-season grass with fine-to-medium gray-green blades that, when growing as a weed in cool-season turf, betrays itself by its wiry above-ground stolons and below-ground rhizomes radiating outward from established patches. Its leaf blades are short and pointed, and a useful diagnostic is the fringe of hairs forming the ligule, which separates it from creeping bentgrass (tall membranous ligule), nimblewill (short membranous ligule), and zoysiagrass (ligule of hairs but coarser texture). The combination of flat, branching stolons rooting at the nodes, thin rhizomes, and a tight, mat-forming habit that spreads in expanding circular patches is characteristic.

Bermudagrass invades cool-season turf as expanding circular patches of finer, gray-green grass that creep over and crowd out the desirable species, and the contrast becomes glaring in fall when the bermudagrass turns straw-brown and dormant while the rest of the lawn remains green, leaving unsightly dead-looking patches. Its dense, mat-forming stolons and rhizomes choke out cool-season grass over time, steadily enlarging the infested area and degrading both the uniformity and the off-season appearance of the stand.

As a weed, bermudagrass is a vigorous warm-season perennial that spreads by three means: seed, above-ground stolons, and below-ground rhizomes. This multi-front vegetative spread, combined with deep, persistent rhizomes, is what makes it so difficult to remove once established. It grows aggressively through the heat of summer and goes dormant and turns brown with cool fall temperatures, regrowing from its rhizomes and stolons the following spring. The persistence of the rhizome reserves means that severing or spraying the tops alone rarely eliminates a stand.

In cool-season lawns, bermudagrass is favored by hot, sunny conditions and by close mowing, which weakens the cool-season turf and lets the heat-loving bermudagrass spread by stolons across thinned, sunny areas. Open, low-mowed, drought- or heat-stressed turf along edges, walkways, and south-facing exposures is most vulnerable, and the weed advances fastest in midsummer when cool-season grasses are under heat stress. It is primarily an aesthetic and competitive problem in cool-season stands because it turns brown and dormant in fall while the surrounding turf stays green.