The New Zealand Plant Conservation Network

Species

Rytidosperma petrosum

Etymology

Rytidosperma: wrinkled seed

Common Name(s)

Cook Strait bristle grass

Current Conservation Status

2012 - At Risk - Naturally Uncommon

Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB

Previous Conservation Status

2009 - At Risk - Naturally Uncommon
2004 - Range Restricted

Qualifiers

2012 - RR, Sp

Authority

Rytidosperma petrosum Connor et Edgar

Family

Poaceae

Flora Category

Vascular - Native

NVS Species Code

RYTPET

Structural Class

Grasses

Synonyms

None

Distribution

Endemic. Cook Strait Region, Kapiti, Stephens and DUrville Islands, South Wellington and Wairarapa Coast to Cape Palliser

Habitat

Predominantly a coastal species, favouring very exposed, dry, sunny, lichen encrusted cliff faces. It dislikes growing in deep soil. Also grows on serpentinite rock near the summit of DUrville Island

Features

Stiff, wiry and rather dense tufted grass forming small tussocks in rock cracks and amongst saxicolous lichens in sunny sites. Tufts forming at ends of elongating shoots, rooting at nodes; leaves less than or equal to culms, more or less pungent, disarticulating at ligule; branching intravaginal. Leaf-sheath glabrous, light grey to dark brown drying straw-yellow to white; apical tuft of hairs 1-1.5 mm. Ligule c.0.5 mm. Leaf-blade to 150 mm, glabrous, stiff, inrolled margins glabrous. Culms to 400 mm internodes glabrous. Raceme or racemose panicle small, erect, to 40 mm, of very few large spikelets on short pedicels; rachis and pedicels almost glabrous with only a few scattered teeth and usually small tufts of long hairs at branch axils. Spikelets 4-6-flowered, awns and sometimes lemma lobes exserted from glumes. Glumes green, lanceolate, acute, 8.5-15 mm more or less equal; lower 5-(7)-nerved, upper 3-nerved. Lemma 2.5-3.5 mm, 9-nerved, upper row of hairs interrupted, dense marginal tufts with few additional hairs adjacent, hairs very much less than lemma lobes, lower row more or less continuous, with dense strong marginal tuffs and less dense tufts between, overlapping upper, glabrous elsewhere; lobes 4.5-8 mm, narrowing to strong awn and often shortly lobed at awn base; central awn 7.5-14 mm, column 2.5-4 mm, less than upper lemma hairs. Callus 0.7-1 mm, strong marginal hair tufts overlapping lower lemma hairs. Rachilla 0.5-0.6 mm. Anthers 0.7-1.5 mm, yellow. Seed 2.5 x 1.0 mm.

Similar Taxa

The coastal, exposed, sunny rock habitat of R. petrosum is very distinctive. The only other bristle grass to exclusively frequent such dry, exposed rock outcrops is R. corinum Connor et Edgar. Rytidosperma corinum is only found well inland in montane to subalpine habitats. It is a mainly South Island species known from one inland North Island site (Kaweka Range). It differs from R. petrosum by the rachis and pedicels which are closely short-scabrid (virtually glabrous in R. petrosum), with hairs at branch axils only slightly longer than the preceeding scabridity (contrasting with the obvious small tufts of long hairs present in R. petrosum) and with the upper lemma hairs more or less continuous (sparse and irregular in R. petrosum).

Flowering

(September -) October (-February)

Flower Colours

Yellow

Fruiting

(November-) January (-July)

Propagation Technique

Easy from fresh seed and rooted pieces. Does best in a very dry, sunny spot with excellent drainage. Good in pots. Dislikes humidity.

Threats

A local endemic, threatened at some mainland sites on the South Wellington coastline by weeds and quarrying. Locally abundant on some offshore islands (e.g., Kapiti), but as a rule very uncommon

Chromosome No.

2n = 48

Endemic Taxon

Yes

Endemic Genus

No

Endemic Family

No

This page last updated on 17 Jan 2014