Knotgrass  (Paspalum distichum)

Knotgrass, is a warm season perennial grass. It is closely related to dallisgrass, P. dilatatum. Knotgrass is found throughout California, except in the Mojave and Sonoran deserts, up to 5400 feet (1650 m). Although it is a good forage grass and is used for controlling erosion in ditches and canal banks, it can be problematic in crops, along water body margins, and in other disturbed places. It is often considered desirable in natural areas; its seeds and leaves serve as forage for numerous animals and birds.

Habitat

Irrigation and drainage ditches, canals, pond and reservoir margins, marshes, riparian areas, moist grassland, seasonal wetlands, stream banks, moist disturbed areas, roadsides, turf, rice fields, irrigated perennial crops, orchards, and vineyards.

Mature plant

Mature knotgrass forms mats and grows up to 2 feet (60 cm) long. The stem is round in cross-section and stems range from erect to prostrate with erect tips. Leaves are flat, often keeled at the base, and hairless except for a few long hairs at the base. Sheaths are open and usually are covered with long hairs. Leaves are rolled in the bud.

Collar region

The edge of the collar usually has a few long hairs. Ligules are membranous and somewhat squared at the top. There are no auricles.

Flowers

Flowers bloom from June through October. The flower head is "V"-shaped, formed by two (sometimes three) branches. The main flowering stem can be up to 6 inches (15 cm) long. The branches grow from about 2/5 to 2-2/5 inches (1–6 cm) long. 

Reproduction

Reproduces from seed and above and belowground creeping stem fragments. All disperse with water, soil disturbance, and agricultural operations.

Related or similar plants

• Dallisgrass, Paspalum dilatatum

More information

• Grass ID illustration
• Calflora's distribution map
• For agriculture: UC IPM Pest Management Guidelines