Epilobium atriplicifolium
Common names
willowherb
Biostatus
Native – Endemic taxon
Category
Vascular
Structural class
Herbs - Dicotyledons other than Composites
Detailed description
Variable, suberect to erect, much-branched, matted, perennial herb 20-360 mm tall, bearing numerous leafy stolons arising from the base; plants with retrorsely (rarely antrorsely) appressed or erect hairs decurrent from the petiole margins, the hairs running out on the margins of leaves, or strigulose all around. Leaves opposite, alternate in the inflorescence, lamina usually much shorter than subtending internodes, sessile or on short petioles up to 2 mm long, dull bluish-green, glabrous except for a few hairs near the base on the margins, the lateral veins not prominent, 2-3 on each side of the midrib; lamina 8-18 x 4-5 mm, narrowly elliptic to ovate, apex acute, base rounded, margins serrulate, with 1-6 teeth on each side. Inflorescence erect, the flowers scattered down the stem. Flowers erect, Ovaries 6-15 mm long, glabrous (rarely weakly to densely strigulose), on pedicels 1-17 mm long. Floral tube 0.5-1.5 mm deep, 0.7-2.2 mm diameter, glabrous or strigulose externally. Sepals 2.0-4.5 x 0.8-1.5 mm, not keeled, glabrous or strigulose. Petals 2.8-6.0 x 1.8-4.5 mm, notch 0.7-2.0 mm deep; white, sometimes flushing pink after pollination. Anthers 0.4-0.9 x 0.25-0.5 mm, cream or yellow; filaments white, those of longer stamens 1.0-2.7 mm long, those of shorter stamens 0.6-1.6 mm long, the anthers of the longer stamens dehiscing first and shedding pollen directly on to the stigma after the flower opens. Styles 1.2-3.2 mm high, white; stigma 0.8-2.6 x 0.3-1.2 mm, white, clavate, surrounded by anthers of at least the longer and usually both sets of stamens at anthesis. Capsule 17-36 mm long, on pedicels 10-90 mm long; blue-green, glabrous (rarely densely strigulose). Seeds 0.7-1.2 x 0.3-0.6 mm, pale orange-brown to orange, obovoid or narrowly obovoid, testa finely reticulate-papillate, apex rounded; coma 5-7 mm long, white, caducous.
Similar taxa
Epilobium atriplicifolium differs from the allied E. alsinoides and E. tenuipes by having finely reticulate-papillate rather than finely reticulate seeds, and pedicels which elongate to 10-90 mm (usually 10-40 mm long) long in fruiting specimens (10-80 mm but usually 20-80 mm in E. alsinoides). It differs from E. elegans, with which it sometimes grows, by its narrower leaves, smaller flowers, and longer-pedicellate condition. From E. cockayneanum, with which it also grows in the Central North Island and South Island, it differs by its taller, less matted growth habit, narrower, less deeply toothed leaves (leaves of E. cockayneanum are broadly ovate, ovate-elliptic to ovate-oblong, 5-14 x 6-8 mm, and more deeply toothed).
Distribution
Endemic. New Zealand: North, South, Stewart, Chatham, Antipodes, Campbell and Auckland Islands.
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 | Not Threatened
Threats
Not Threatened. However, E. atriplicifolium is seemingly scarce (apparently naturally so) north of the Waikato.
Detailed taxonomy
Family
Synonyms
Epilobium alsinoides subsp. atriplicifolium (A.Cunn.) P.H.Raven et Engelhorn
Taxonomic notes
Raven & Raven (1976) adopted a very conservative treatment for New Zealand Epilobium. In that treatment they recognised Epilobium atriplicifolium and E. tenuipes as subspecies of E. alsinoides. They also included with E. alsinoides subsp. atriplicifolium, E. cockayneanum (treated as a species here) and within subsp. tenuipes they merged E. elegans (also accepted at species rank here). Raven & Raven (1976) argued for subspecies rank and species merger on the basis of what they saw as intergrading forms between E. atriplicifolium, E. cockayneanum, E. elegans and E. tenuipes in the South Island. They did note that intergrading was not evident in the North Island, where the “major entites…are sharply distinct” but they suggested that this had to do with the effectively autogamous breeding system of these taxa, and while they accepted that intergrading forms occurred within the most “highly disturbed vegetational formation in New Zealand” (i.e. tussock grasslands) suggesting that such intergrades were not natural, they nevertheless felt justified in their highly conservative treatment. Subsequently field botanists have largely followed the unpublished views of the late Tony Druce who continued to recognise as species E. atriplicifolium, E. cockayneanum, E. elegans and E. tenuipes. For want of a thorough, multi-marker DNA-based revision of New Zealand Epilobium, for now at least it seems preferrable to follow Druce (1993) rather than Raven & Raven (1976), whose treatment of Epilobium, whilst understandable for its time, seems inconsistent (see also comments under E. cockayenanum).
Endemic taxon
Yes
Endemic genus
No
Endemic family
No
Ecology
Flowering
November - March
Fruiting
January - May
Life cycle and dispersal
Minute pappate seeds are wind dispersed (Thorsen et al., 2009).
Propagation technique
Easily grown from fresh seed and rooted pieces. Dislikes humidity and prone to powdery mildew in humid climates. Inclined to be weedy.
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]
FACU: Facultative Upland
Occasionally is a hydrophyte but usually occurs 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.
atriplicifolium: Leaves resembling Atriplex, unrelated plant
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.
EPIATR
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 | Not Threatened
2012 | Not Threatened
2009 | Not Threatened
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 | Regionally Not Threatened
Referencing and citations
References and further reading
Druce, A.P. 1993: Indigenous vascular plants of New Zealand. Ninth Revision. Unpublished Checklist held at Landcare Research, Lincoln, New Zealand.
Raven, P.H.; Raven, T.E. 1976: The genus Epilobium in Australasia. New Zealand DSIR Bulletin 216. Wellington, Government Printer.
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.
Webb, C.J.; Simpson, M.J.A. 2011: Seeds of New Zealand Gymnosperms and Dicotyledons. Christchurch, Manuka Press.
Attribution
Fact sheet prepared for NZPCN by P.J. de Lange (22 October 2012). Description adapted from Raven & Raven (1976).
NZPCN Fact Sheet citation
Please cite as: de Lange, P.J. (Year at time of access): Epilobium atriplicifolium Fact Sheet (content continuously updated). New Zealand Plant Conservation Network. https://www.nzpcn.org.nz/flora/species/epilobium-atriplicifolium/ (Date website was queried)