Rytidosperma petrosum
Common name
Cook Strait bristle grass
Synonyms
None
Family
Poaceae
Flora category
Vascular – Native
Endemic taxon
Yes
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.
RYTPET
Chromosome number
2n = 48
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) – more information about this can be found on the NZTCS website. This report includes a statistical summary and brief notes on changes since 2012 and replaces all previous NZTCS lists for vascular plants.
Please note, threat classifications are often suggested by authors when publications fall between NZTCS assessment periods – an interim threat classification status has not been assessed by the NZTCS panel.
- Conservation status of New Zealand indigenous vascular plants, 2017 . 2018. 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. Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Naturally Uncommon | Qualifiers: RR, Sp
Previous conservation statuses
2012 | At Risk – Naturally Uncommon | Qualifiers: RR, Sp
2009 | At Risk – Naturally Uncommon
2004 | Range Restricted
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.
Detailed description
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. Inflorescence a 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 × 1.0 mm.
Manaaki Whenua Online Interactive Key
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.
Etymology
rytidosperma: Wrinkled seed
Where To Buy
Not commercially available
Attribution
Description modified from Edgar and Connor (2000).
References and further reading
Edgar E, Connor HE. 2000. Flora of New Zealand. Vol. V. Grasses. Manaaki Whenua Press, Christchurch, NZ. 650 p.