Species

Paspalum distichum

Etymology

Paspalum: The Greek name for millet

Common Name(s)

mercer grass

Authority

Paspalum distichum L.

Family

Poaceae

Brief Description

Floating grass forming dense mats, with typical two-pronged lowerheads produced in summer

Flora Category

Vascular - Exotic

NVS Species Code

PASDIS

The National Vegetation Survey (NVS) Databank is a physical archive and electronic databank containing records of over 94,000 vegetation survey plots - including data from over 19,000 permanent plots. NVS maintains a standard set of species code abbreviations that correspond to standard scientific plant names from the Ngä Tipu o Aotearoa - New Zealand Plants database.

Structural Class

Grasses

Synonyms

Paspalum paspalodes

Distribution

Locally common in the North Island but also in the South Island as far south as Canterbury.

Habitat

Still and slow flowing water bodies and wetland margins.

Features

Creeping, perennial, mat-forming grass, the stems sprawl along the ground and then grow to 60 cm tall. Stolons long, rooting frequently, with rhizomes. Leaves are distantly alternate, the lamina is 4-10 cm long and 2-6mm wide, tip pointed, bluish-green, soft and lax, slightly hairy above and below, rolled and hairy at base. Ligule up to 4 mm, membrane-like, whitish-translucent, often torn. Auricle absent. Sheath with reddish-purple tinge. Seedhead of 2 (sometimes 1 or 3) diverging, erect racemes, 25-50 mm long; with softly hairy spikelets.

Similar Taxa

Kikuyu grass (Pennisetum clandestinum). Differs from Mercer grass in that Kikuyu grass lacks a membranous ligule and has a short flowering head that is almost enclosed within the leaves. In contrast, Mercer grass has a very distinctive forked flowering head.

Flowering

November, December, January, February

Flower Colours

Green

Fruiting

Late summer

Year Naturalised

1887

Origin

Europe

Reason for Introduction

Forage grass for wet areas

Control Techniques

Not usually controlled in New Zealand, but may be controlled by mowing or herbicidally.

Life Cycle and Dispersal

Perennial. Reproduces by seed and stem fragmentation. Seeds freely, seed viability unknown. Dispersed by water, livestock pelts and hooves (possibly seed in dung). Contaminated diggers and dumped vegetation.

Tolerances

Tolerates wet, hot to mod-cool, wind, damage and grazing, most soils. Intolerant of frost, deep shade and dry conditions.



Attribution

Factsheet prepared by Paul Champion and Deborah Hofstra (NIWA).

References and further reading

Champion et al (2012). Freshwater Pests of New Zealand.  NIWA publication. http://www.niwa.co.nz/freshwater-and-estuaries/management-tools/identification-guides-and-fact-sheets/freshwater-pest-species.

This page last updated on 18 Mar 2015