Epilobium petraeum
Common name
rock willow herb
Synonyms
None
Family
Onagraceae
Flora category
Vascular – Native
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Structural class
Herbs - Dicotyledons other than Composites
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 | Sparse
Distribution
Endemic. South Island from the Kaikoura Ranges (Mt Fyffe) south to the Mt Cook Region of Canterbury.
Habitat
A species of exposed, steep, partially stable, sparsely vegetated greywacke rock outcrops, stable to partially stable scree in and near margins of rock outcrops, and occasionally found on partially stable and exposed stream margins.
Detailed description
Compact, densely spreading, glabrous herb producing shrublets up to 400 x 100 mm. Old stems prostrate to spreading; new stems erect, red; not rooting at nodes. Petiole 5-7 mm, slender, channelled, appressed to the stem or slightly spreading. Leaves 15-24 x 4-7 mm, opposite, ovate, elliptic, or broad-elliptic, glossy, erect or spreading, longer than internodes, 3-5 teeth on each margin, upper surfaces dark-green and sometimes flushed red, uppersides red, margin and midrib usually red, base cuneate, apex obtuse to retuse. Inflorescence terminal, conspicuous; flowers perfect, erect; pedicel 2-4 mm long, green; bud pink. Sepals 4, 4-4.5 x 1.2-1.4 mm, oblong, not keeled, red, apex acute. Petals 4, 5-6 x 1.9-2.1 mm, obovate, white, apex notch 0.5-0.8 mm deep. Floral tube 1-1.2 mm deep, c. 2 mm wide. Ovary 12-14 mm, green; style 2.3 mm, white; stigma 1 x 0.4 mm, yellow; filaments white, unequal, longer 2-2.5 mm, shorter 1-1.2 mm. Capsule 35-55 x 1.4-1.8 mm, scarlet-red; pedicel 10-24 mm, scarlet-red. Seeds 1-1.1 x 0.4-0.45 mm, pale brown, papillose but usually flat on one surfave; proximal end constricted with acute apex; chalazal end with a very short, inconspicuous neck; coma 4-5 mm long, white, caducous.
Similar taxa
Distinguished by the low, spreading, compact habit, all parts glabrous, red stems, opposite, dark-green and glossy leaves with the upper midrib usually red, the leaves not obscuring the internodes, a floral tube 1-1.2. mm deep, and papillose 1-1.1. x 0.4-0.45 mm seeds with a non-persistent coma. It is most similar to E. brevipes Hook.f. which is a glabrescent shrub of similar habitats, with leaves that are initially opposite becoming alternate toward the stem apices. The leaves are narrowly elliptic to elliptic with acute rather than obtuse to retuse apices. A key difference is that the leaf apex in E. breivpes has a distinct apiculus (like a lump of gum) which is absent in E. petraeum. Furthermore the stem leaf junction of E. brevipes has a miniscule tuft of strigulose hairs.
Flowering
December - January
Flower colours
White
Fruiting
January - March
Life cycle
Minute pappate seeds are wind dispersed (Thorsen et al., 2009).
Propagation technique
Easily grown in a pot kept in an alpine house or in a rock garden. Prefers a fertile, free draining soil and full sun. Intolerant of warm, humid climates.
Threats
A widespread, naturally uncommon, biological sparse species of high alpine rock habitats. There is no evidence of decline.
Etymology
epilobium: From the Greek epi- ‘upon’ and lobos ‘a pod’, the flowers appearing to be growing on the seed pod.
petraeum: Loves rocks
Where To Buy
Not commercially available
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange 6 June 2004. Description adapted from Heenan (1996).
References and further reading
Heenan, P. B. 1996: Epilobium petraeum (Onagraceae), a new species of alpine willow-herb from New Zealand. New Zealand Journal of Botany 34(1): 41-45.
Thorsen, M. J.; Dickinson, K. J. M.; Seddon, P. J. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285-309
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Epilobium petraeum Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/epilobium-petraeum/ (Date website was queried)