Paspalum dilatatum aka Dallis Grass

Paspalum dilatatum, or Dallis grass, belongs to the grass family. Its native range runs from southeastern and southern Brazil to northern Argentina. This perennial forms dense clumps in lawns and disturbed ground. It also grows in moist grassland and along waterways. Outside its native range, it can become an invasive weed. Its thick growth can crowd out native plants.

Plants reach about 3.3 feet [1 m] in height. Reported stems range from 1 to 5.9 feet [0.3–1.8 m]. Short rhizomes spread beneath the soil and bear clustered stems. These stems stand upright or lean upward. They can root at joints that touch the ground. Thick, fibrous roots may reach 3.9 feet [1.2 m] deep. The green leaves form a coarse, spreading tuft. Their smooth blades contrast with hairy lower sheaths. Stem bases and leaf sheaths may show red or purple. Each leaf has a thin, membranous ligule at its base.

Flowers appear from May to November in the NC State account. Several short racemes branch near the top of each stalk. They spread outward and may droop as they develop. Small, paired spikelets range from pale green to purple. Wind carries the pollen. Flat, egg-shaped seeds line the flowering branches in two rows. The brown fruits are achenes. Plants make many seeds, which drive their spread. Some birds use the plant as a food source.

Full sun suits this grass best, though it accepts light shade. It grows in a broad range of moderately fertile soils. Moist ground suits it best, including loam and sand. Established plants withstand both drought and brief floods. It prefers acid to neutral soil but tolerates a wider pH range. NC State lists USDA zones 6–9. Useful Tropical Plants reports dormant roots surviving about 14°F [−10°C]. Young growth may suffer severe harm at 27°F [−3°C]. Warm, moist climates with short dry seasons suit it best.

People grow Dallis grass for summer pasture and soil erosion control. These uses come with a strong risk of unwanted spread. NC State lists it as invasive in several southeastern states. Digging young plants before seed set helps limit new patches. Rhizomes left underground can grow again after removal. Ergot fungus can infect the seed heads and poison livestock. This hazard matters where people use it as forage. Useful Tropical Plants lists no known human food or medicinal uses.