T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Paspalum distichum (Mercer grass)

Kingdom: Plantae
Division: Magnoliophyta
Class: Liliopsida
Order: Poales
Family: Poaceae
Subfamily: Panicoideae
Tribe: Paniceae
Gender: Paspalum
Species: P. distichum
Binominal name: Paspalum distichum
Synonym: Paspalum paspalodes
Common names: Water Couch, Knot Grass, Knotgrass, Mercer grass, Buffalo quick paspalum, Couch Paspalum, Jointgrass, Dich-grass, Silt grass, Devils grass, Wiregrass, Seaside millet, Ginger grass, Victoria grass, Thompsom grass, Seashore paspalum, Water couch, Dallisgrass, Water finger-grass

Paspalum distichum is a plant in the family of the Poaceae. It is a fast-growing, perennial, rhizomatous grass of wet areas, growing 0.05-0.5 m high. Its native range is obscure as it is found on most continents. It was introduced into New Zealand as a forage grass for wet areas. In New Zealand, it is locally common on the North Island. In the South Island, it grows as far south as Canterbury. Its habitats are still and slow flowing water bodies, often saline and wetland margins where it can form dense floating mats preventing recruitment, blocking waterways which causes flooding. Rotting vegetation also affects water quality. It is spread by seeds, stolons and rhizome fragments, via water, livestock pelts, hooves, possibly seeds in dung and contaminated machinery, dumped vegetation and soil movement. Irrigation canals are particularly prone to be overgrown by this plant.

Paspalum distichum leaves have a pointed tip and are 40-150 mm long and are 3-8 mm wide. They are a bluish-green colour, soft and lax, slightly hairy above and below, rolled and hairy at base. The ligule is up to 4 mm long, membrane-like, whitish-translucent, often torn. There is no auricle.
In summer a very distinctive forked flowering head of 2 diverging, erect racemes, >6 cm long; with softly hairy spikelets develop on the end of 20-50 cm long stalks. The small flowers are green/green-purple coloured.

A photo of the very distinctive forked flowering head of 2 diverging, erect racemes.

The leaf.

The ligule,

The roots

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0