Paspalum distichum
Common name
Mercer grass
Synonyms
Paspalum paspalodes
Family
Poaceae
Flora category
Vascular – Exotic
Structural class
Grasses
NVS code
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.
PASDIS
Conservation status
Not applicable
Brief description
Floating grass forming dense mats, with typical two-pronged lowerheads produced in summer
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.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland).
FACW: Facultative Wetland
Usually is a hydrophyte but occasionally found in uplands (non-wetlands).
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
Life cycle
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.
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.
Tolerances
Tolerates wet, hot to mod-cool, wind, damage and grazing, most soils. Intolerant of frost, deep shade and dry conditions.
Etymology
paspalum: The Greek name for millet
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.