Epilobium insulare
Common names
willowherb
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Detailed description
Loosely matted flaccid perennial herb, often much-branched, the stems 30–400 mm tall, creeping and rooting near the base; stems usually straw-coloured, strigulose all round least in the upper portions, with an admixture of glandular hairs in the inflorescence. Leaves much shorter than the internodes they subtend, opposite, alternate in the inflorescence, dull bluish-green, paler and occasionally slightly glaucous beneath (often tinged reddish especially along the lamina margin), the lateral veins visible, usually 2–3 on each side of the midrib; lamina 4–26 × 4–14 mm, narrowly to overy broadly ovate, apex acute or obtuse, base rounded, margins remotely, shallowly or rarely prominently serrulate, usually with 3–10 teeth on each margin; petioles distinct, 10–30 mm long. Inflorescence erect. Flowers erect. Ovaries 10–18 mm long, glandular and strigulose, on a pedicel 2–11 mm long. Floral tube 0.9–1.2 × 1.3–1.7 mm. Sepals 2.0–3.5 × 0.8–0.9 mm, weakly keeled, glandular and strigulose. Petals 3.3–6.2 × 1.6–3.5 mm, notch 0.7–2.0 mm deep, white. Stamen filaments white, of two types: long (1.2–3.0 mm long) and short (0.45–1.5 mm long). Anthers 0.3–1.0 × 0.3–0.5 mm, cream. Style 1.7–2.3 mm long, white tinged pink near the base, stigma 0.8–1.8 × 1.0–1.7 mm, broadly clavate surrounded by both or occasionally only the longer stamens at anthesis. Capsule 25–55 mm long, sparsely strigulose and glandular, on a pedicel 5–65 mm long. Seeds 0.8–1.1 mm long, orange to orange-brown, elliptic-oblong to elliptic-obovate, finely reticulate and scarcely to distinctly mamillate; coma 4–6 mm long, white, caducous.
Similar taxa
Epilobium insulare is most often confused with E. chionanthum especially as both species grow in similar habitats and are morphologically superficially similar. Indeed Raven & Raven (1976) venture the hypothesis that E. insulare is either a species that has evolved through hybridisation with E. alsinoides and E. chionanthum, or that it is an autogamous derivative of the mostly outcrossing, larger flowered and seeded E. chionanthum. From E. chionanthum, E. insulare is distinguished by its young stems which are evenly strigulose hairy all round rather than mostly glabrous, and where strigulose then only along lines decurrent from the margins of the petioles, distinctly red-margined leaves, smaller, more prominently notched petals (3.3–6.2 × 1.6–3.5 mm with the notch 0.7–2.0 mm deep in E. insulare; 6.0–11.0 × 4.5–6.0 mm with the notch 0.8–1.3 mm deep in E. chionanthum), and by the smaller seeds (0.8–1.1 mm long in E. insulare 1.4–1.8 mm long in E. chionanthum), and a white rather than grey coma.
Distribution
Endemic. New Zealand: North Island (from the Waikato River mouth and Bay of Plenty south), South Island, Chatham Islands.
Habitat
Relatively open, marshy places; bogs, and about lake margins; sea level to 900 m.
Current conservation status
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2023 | At Risk – Declining | Qualifiers: Sp, DPS, DPT, RR
Detailed taxonomy
Family
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
November–March
Fruiting
January–April
Life cycle and dispersal
Minute pappate seeds are wind dispersed (Thorsen et al., 2009).
Propagation technique
Easily grown from fresh seed and rooted pieces. Does best when planted into a swamp or within a pot partially immersed in a pond.
Wetland plant indicator status rating
Information derived from the revised national wetland plant list prepared to assist councils in delineating and monitoring wetlands (Clarkson et al., 2021 Manaaki Whenua – Landcare Research Contract Report LC3975 for Hawke’s Bay Regional Council). The national plant list categorises plants by the extent to which they are found in wetlands and not ‘drylands’. The indicator status ratings are OBL (obligate wetland), FACW (facultative wetland), FAC (facultative), FACU (facultative upland), and UPL (obligate upland). If you have suggestions for the Wetland Indicator Status Rating, please contact: [Enable JavaScript to view protected content]
OBL: Obligate Wetland
Almost always is a hydrophyte, rarely in uplands (non-wetlands).
Other information
Where To Buy
Not commercially available.
Etymology
epilobium: From the Greek epi- ‘upon’ and lobos ‘a pod’, the flowers appearing to be growing on the seed pod.
insulare: From the Latin insula ‘island’, pertaining to or growing on islands
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.
EPIINS
Chromosome number
2n = 36
Previous conservation statuses
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2022-2023 using the New Zealand Threat Classification System (NZTCS) – more information about this can be found on the NZTCS website. This report includes replaces all previous NZTCS lists for vascular plants. Previous assessments can be found here.
- Conservation status of vascular plants in Aotearoa New Zealand, 2023. 2024. Peter J. de Lange, Jane Gosden, Shannel P. Courtney, Alexander J. Fergus, John W. Barkla, Sarah M. Beadel, Paul D. Champion, Rowan Hindmarsh-Walls, Troy Makan and Pascale Michel Department of Conservation. Source: NZTCS and licensed by DOC for reuse under the Creative Commons Attribution 4.0 International licence.
2017 | At Risk – Declining | Qualifiers: DP, RR, Sp
2012 | Data Deficient | Qualifiers: RR
2009 | At Risk – Declining | Qualifiers: DP, RR
2004 | Not Threatened
Regional conservation statuses
The regional threat classification system leverages off the national assessments in the NZTCS, providing information relevant for the regional context. Otago conservation status information is sourced from the “Regional conservation status of indigenous vascular plants in Otago” Jarvie S et al. (2024) report.
Otago: 2024 | Threatened – Regionally Vulnerable | Qualifiers: DPR, DPS, DPT, NR, RR, Sp, TL
Referencing and citations
References and further reading
Raven PH, Raven TE. 1976. The genus Epilobium in Australasia. New Zealand DSIR Bulletin 216. Government Printer, Wellington, NZ. 321 p.
Thorsen MJ, Dickinson KJM, Seddon PJ. 2009. Seed dispersal systems in the New Zealand flora. Perspectives in Plant Ecology, Evolution and Systematics 11: 285–309. https://doi.org/10.1016/j.ppees.2009.06.001.
Webb CJ, Simpson MJA. 2001. Seeds of New Zealand Gymnosperms and Dicotyledons. Manuka Press, Christchurch. 428 p.
Attribution
Fact Sheet Prepared for NZPCN by: P.J. de Lange 28 August 2011. Description adapted from Raven & Raven (1976) and Webb & Simpson (2001).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Epilobium insulare Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/epilobium-insulare/ (Date website was queried)