Epilobium angustum
Common names
willowherb
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Simplified description
Perennial herb. Habit creeping to mat forming. Leaves opposite, oval to ovate, rugose impressed on the upper surface. Pedicels and flowers generally erect. Capsules, pedicels and sepals sparsely to densely hairy. Internodes with few hairs, mostly in decurrent lines from the petioles on the newer growth.
Flower colours
White
Detailed description
Small mat forming perennial herb, sometimes forming a dense turf. Stems creeping, with sparse glandular, round tipped hairs ascending or spreading, generally in two decurrent lines from the petioles, and mostly confined to the newer growth, sometimes also with scattered appressed hairs. Leaves opposite, entire, petiole to 1.5mm or subsessile, with 1-3 widely spaced and poorly defined teeth, 1.5-12mm long by 1-5mm wide, up to four lateral veins visible, oblong, ovate, or obovate in shape. Base of leaf attenuate to obtuse, apex subacute to obtuse. Upper leaf surface rugose-impressed and shiny, with the lower leaf surface smooth and dull. Leaves crowded and imbricate, but sometimes distant, copper coloured to green, often reflexed. Flowers held upright, borne individually from leaf axils. Ovaries, floral tube and sepals sparsely to densely hairy, pedicel sparsely hairy. Pedicels 2-6mm at flowering, elongating to 7-50-(80)mm as capsule matures. Ovaries 4-7-(10)mm, dull, green to red-brown. Floral tube 1.1-2.5mm across, 0.6-3mm deep. Sepals 0.7-1.3mm wide, 1.1-4mm long, lacking a keel. Petals 1.4-5.8mm wide, 2.9-8mm long, with a notch 0.7-1.6 mm deep, white. Stamens of two types, short and long, longer ones 0.6-3.5mm, shorter ones 0.2-1.2mm. Anthers yellow, 0.3-0.6mm by 0.5-1.3mm long. Stigma clavate to capitate 0.45-1mm wide by 0.7-1.2mm high, on a white style 1.1-7mm long. Capsules cylindrical and finely torulose, sparsely to densely hairy, 7-13-(16)mm long. Seeds smooth, 0.4-0.5mm wide, 0.75-0.95mm long, light-brown in colour, with swollen, translucent and cellular ventral surfaces, this being more obvious at the base and apex of the seed. The coma is 4-5mm, and is easily removed.
Similar taxa
Similar to other small creeping Epilobium species; particularly E. brunnescens and E. komarovianum, both of which can be found in similar habitats. The species differs from E. brunnescens, and all other small Epilobium species except E. komarovianum, by having rugose-impressed (dimpled) upper leaf surfaces. Epilobum angustum differs from E. komarovianum (which also has rugose-impressed upper leaf surfaces) by the presence of glandular pubescence on the pedicel, ovary, sepals, and capsules. Those of E. komarovianum are subglabrate to very sparsely eglandular hairy. The seeds of E. komorovianum also lack the swollen ventral cellular rim of E. angustum. Epilobium komarovianum can often be found growing with E. angustum, but is more often in a band of slightly dryer higher ground, around pond and lake margins, sometimes decending into the wetter habitat of E. angustum.
Distribution
Endemic. South Island, east of the main divide from Marlborough to Fiordland.
Habitat
In the short turf around the margins of lakes and tarns and other seasonally inundated hollows of glacial origin; 180-820m. Generally in open clay or stony areas in places that are periodically inundated with water, barely venturing far into the surrounding tussock grassland.
Substrate details
Mostly greywacke glacial debris clay and loess.
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: DPS, DPT, RR
Threats
The species is threatened by intensification of farming practices and land modification in some of the dryland areas where it most commonly occurs. These practices help destroy its habitat through ploughing, pugging, and other disturbance, as well as allowing the infiltration of more competitive exotic weed species into the delicate turf communities in which the species lives.
Detailed taxonomy
Family
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
November to April
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
Etymology
epilobium: From the Greek epi- ‘upon’ and lobos ‘a pod’, the flowers appearing to be growing on the seed pod.
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.
EPIANG
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 – Naturally Uncommon | Qualifiers: DP, RR
2012 | At Risk – Naturally Uncommon | Qualifiers: RR
2009 | Not Threatened
2004 | Not Threatened
Regional conservation statuses
Otago: 2024 | Threatened – Regionally Endangered | Qualifiers: DPS, DPT, NR, PF, RR, Sp
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.
Referencing and citations
References and further reading
Raven, P.H.; Raven, T.E. 1976: The genus Epilobium in Australasia. New Zealand DSIR Bulletin 216. Wellington, Government Printer.
Attribution
Fact sheet prepared by Rowan Hindmarsh-Walls for NZPCN (06 May 2020). Description adapted from Raven & Raven (1976).
NZPCN Fact Sheet citation
Please cite as: Hindmarsh-Walls, R. (Year at time of access): Epilobium angustum Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/epilobium-angustum/ (Date website was queried)