Paspalum orbiculare
Common name
scrobic
Synonyms
New Zealand plants have long been incorrectly equated with Paspalum scrobiculatum L., a quite unrelated Indian annual species
Family
Poaceae
Flora category
Vascular – Native
Endemic taxon
No
Endemic genus
No
Endemic family
No
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.
PASORB
Chromosome number
2n = 63
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2017 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants. Authors: By Peter J. de Lange, Jeremy R. Rolfe, John W. Barkla, Shannel P. Courtney, Paul D. Champion, Leon R. Perrie, Sarah M. Beadel, Kerry A. Ford, Ilse Breitwieser, Ines Schönberger, Rowan Hindmarsh-Walls, Peter B. Heenan and Kate Ladley.
2018 | Threatened – Nationally Vulnerable
Previous conservation statuses
2012 | At Risk – Declining | Qualifiers: DP, SO
2009 | At Risk – Declining | Qualifiers: SO, DP
2004 | Gradual Decline
Distribution
Indigenous. Known only from the Kermadec Islands and North Island of New Zealand. In the North Island it occurs from Northland to Raglan Harbour in the west and Whale Island in the Bay of Plenty. Common in the wider Pacific and Australia
Habitat
Coastal to lowland, in seasonal wetlands (often with Baumea juncea), on lake margins, in gumland scrub, along track sides and near or around active geothermal vents
Features
Perennial grass. Leaves stiffly erect. Leaf sheath subcoriaceous, striate, strongly keeled, brown to purple-brown or red, glabrescent. Ligule 1-2 mm, truncate, entire. Leaf-blade 100-200(-300) x 3.5-5 mm, flat, rigid, midrib distinct, upper surface glabrous, undersides pilose hairy near ligule. Culm (200-)350-700 mm, erect, compressed, internodes glabrous, striate. Panicle erect, 60-120 mm, with 3-8 erect to slightly spreading racemes. Racemes (20-)30-40 mm, 1.2-1.7 mm wide, with short white hairs at base, bearing 2 rows of single to paired, subsessile spikelets. Spikelets 2-2.5 mm, imbricate, ovoid-elliptic to ovoid-orbicular, glabrous, obtuse, light brown. Lower glume 0, upper = spikelet, 3(-5)-nerved, glabrous. Lower floret 3-5-nerved, glabrous. Upper floret elliptic-orbicular, glossy, brown. Flowers with anthers 1 mm, if bearing pollen then yellow, usually brown due to malformed pollen, stigmas purple, seed > 1mm.
Similar taxa
Easily distinguished from the other natrualised species of Paspalum present in New Zealand by the glabrous spikelets. Of those species it is most likely to be confused with P. dilatatum Poir., with which it often grows. P. dilatatum differs by its larger, floppy leaves, larger, drooping panicle, and by the larger spikelets (3-3.5 mm).
Flowering
May flower throughout the year but most plants can be found in flower from August - April
Flower colours
Brown, Yellow
Fruiting
Seed may be present at anytime of the year but it is most commonly found from September - July
Propagation technique
Easy from the division of whole plants and seed but not especially attractive. Very tolerant of waterlogged or drought prone, infertile soils. New Zealand plants are apomictic and appear to produce very little viable seed (< 10% of all seed produced is viable).
Threats
Formerly widespread from Te Paki south to the Bay of Plenty. This species is now scarce south of Auckland City, and has it strongholds on Great Barrier Island and in the far North. It seems to be threatened by other taller, faster growing grass and shrub species, though exact data on the nature or mechanism of its decline is not available. Some populations have been lost accidentally through failure to recognise its indigenous status, or by revegetation projects using taller native species which eventually shading out this grass.
Etymology
paspalum: The Greek name for millet
orbiculare: Icular, circular
Taxonomic notes
Treated as naturalised by the New Zealand Grass Flora (N.Z. Flora Series Vol. V) on the basis of comments made by Cameron (1998), an assessment since shown to be erroneous (de Lange & Murray 2002). Paspalum orbiculare was first collected in New Zealand in 1769 from the Bay of Islands by Banks & Solander, it is widespread from Australia across the Pacific Basin, and has sticky, bird dispersed seeds. New Zealand plants match more closely those from eastern Australia, Lord Howe and Norfolk Islands (de Lange & Murray 2002) than they do those from the Polynesian Islands, thus the argument used by Cameron (1998) that New Zealand plants were established here accidentally as stowaways on Polynesian canoes (waka) seems unlikely.
Attribution
Fact Sheet Prepared by P.J. de Lange (1 November 2009). Description based on Edgar & Connor (2000). See also comments by de Lange & Murray (2002).
References and further reading
de Lange, P.J.; Murray, B.G. 2002: Contributions to a chromosome atlas of the New Zealand flora—37. Miscellaneous families. New Zealand Journal of Botany 40: 1-23
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Paspalum orbiculare Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/paspalum-orbiculare/ (Date website was queried)