Glyceria maxima
Common name
Floating sweetgrass, reed sweetgrass
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.
GLYMAX
Brief description
Robust bright green grass, up to nearly 2 m tall, with creeping rhizomes that form large patches excluding all other plants. The tip of the leaf is boat-shaped. The seedheads are open and branched with many spikelets. The sheath has obviously cross veins.
Distribution
Widely naturalised, abundant in most lowland parts of North Island, more scattered and absent from much of South Island.
Habitat
Aquatic in drains and other slow flowing waterbodies, often forming dense floating mats in open frost-free areas. Also in swamps.
Features
A perennial aquatic grass, to 1.8 m tall. It has an extensive root system up to c. l m deep, as well as sprawling underground stems. The leaves are shiny, hairless and mid-green in colour. They grow 30-60 cm above the water surface and are 0.7-2 cm wide. Leaves end in an abrupt point and their edges are rough to touch. The flower head is open, branched, and 15-45 cm long comprising a large number of spikelets that range from yellow to green in colour, with a purplish tinge. Flowering occurs in spring and summer. Small dark brown seeds are produced prolifically throughout summer and autumn.
Similar taxa
Glyceria declinata and G. fluitans. Both of the other Glyceria species present in New Zealand are much smaller (up to 50 cm tall) with narrow sparingly branched, distinctively brown seedheads and form low clumps as opposed to the tall erect clumps formed by reed sweetgrass.
Flowering
Spring/summer.
Flower colours
Green
Fruiting
late spring-autumn
Life cycle
Perennial.Spread by seed and rhizomes. Prolific seed production. Seeds and rhizome via water flow. Contaminated diggers, livestock, soil movement, dumped vegetation, eel nets, boats and trailers all spread seed and fragments into new catchments.
Year naturalised
1906
Origin
Europe
Reason for introduction
Pasture species
Control techniques
Can be controlled manually, mechanically or herbicidally depending on situation.
Tolerances
Tolerant to physical damage, grazing and pollutants. Intolerant of heavy frost and shade.
Etymology
glyceria: From the Greek glykos ‘sweet’.
Attribution
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.
Coffey BT, Clayton JS (1988). New Zealand water plants: a guide to plants found in New Zealand freshwaters. Ruakura Agricultural Cente. 65pp.
Johnson PN, Brooke PA (1989). Wetland plants in New Zealand. DSIR Field Guide, DSIR Publishing, Wellington. 319pp.
Champion et al (2010). An illustrated guide to common grasses, sedges and rushes of New Zealand. NZ Plant Protection Society Inc, 182pp.