Epilobium is a genus of flowering plants in the family Onagraceae, containing about 197 species. The genus has a worldwide distribution. It is most prevalent in the subarctic, temperate and subantarctic regions, whereas in the subtropics and tropics Epilobium species are restricted to the cool montane biomes, such as the New Guinea Highlands.
The taxonomy of the genus has varied between different botanists, but the modern trend is to include the previously recognised genera Boisduvalia, Chamaenerion (previously Chamerion), Pyrogennema and Zauschneria within Epilobium according to Peter H. Raven, who has extensively studied the willowherbs and merges the other segregate genera into Epilobium. Fringed willowherb (Epilobium ciliatum) is likely a cryptic species complex; apparently these plants also commonly hybridize with their congeners.Bleeker et al. (2007)
Most species are known by the common name willowherbs for their willow-like leaves. Those that were once separated in Boisduvalia are called spike-primroses or boisduvalias. Those Epilobium species previously placed in the Chamaenerion group are known as fireweeds.
Description
Epilobium are mostly herbaceous plants, either annual or perennial; a few are subshrubs. The leaves are opposite or rarely whorled, simple and ovate to lanceolate in shape. The flowers are actinomorphic (radially symmetrical) with four petals that may be notched.Webb, D.A., Parnell, J. and Doogue, D. 1996. An Irish Flora. Dundaldan Press (W. Tempest) Ltd, Dundalk. These are usually smallish and pink in most species, but red, orange or yellow in a few. The fruit is a slender cylindrical capsule containing numerous seeds embedded in fine, soft silky fluff which disperses the seeds very effectively in the wind.
A number of Epilobium species with slightly asymmetrical (zygomorphic) magenta flowers and alternate leaves are placed in the genus Chamaenerion, which may be further separated by some authorities into a genus Chamerion. However, Chamerion is not universally accepted.
Taxonomy It was described by Carl Linnaeus in 1753 based on previous work by Johann Jacob Dillenius.Linné, Carl von, & Salvius, Lars. (1753). Caroli Linnaei ... Species plantarum :exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specificis, nominibus trivialibus, synonymis selectis, locis natalibus, secundum systema sexuale digestas... (Vol. 1, p. 347). Impensis Laurentii Salvii. https://www.biodiversitylibrary.org/page/358366 The type species is Epilobium hirsutum Epilobium L. (n.d.). International Plant Names Index. Retrieved September 20, 2026, from https://www.ipni.org/n/30000954-2 Etymology The genus name derives from the Greek words "epi" meaning "upon" and "lobos" meaning "lobe", with reference to position of the petals above the ovary. Species The following species are recognised in the genus Epilobium:
Epilobium × abortivum Epilobium × aggregatum Epilobium aitchisonii Epilobium algidum Epilobium alpestre Epilobium alsinifolium – chickweed willowherb Epilobium alsinoides Epilobium × amphibolum Epilobium amurense Epilobium anagallidifolium – alpine willowherb, pimpernel willowherb Epilobium anatolicum Epilobium anglicum Epilobium angustifolium Epilobium angustum Epilobium arcticum – Arctic willowherb Epilobium × argillaceum Epilobium arvernense Epilobium × aschersonianum Epilobium astonii Epilobium atlanticum Epilobium australe Epilobium barbeyanum Epilobium billardiereanum – glabrous willowherb Epilobium blinii Epilobium × boissieri Epilobium × borbasianum Epilobium × brachiatum Epilobium brachycarpum – tall willowherb, tall annual willowherb, tall fireweed, panicled willowherb Epilobium brevifolium Epilobium brevipes Epilobium × brevipilum Epilobium brevisquamatum Epilobium × brunnatum Epilobium brunnescens – New Zealand willowherb Epilobium campestre – pygmy willowherb, smooth boisduvalia Epilobium canum – Zauschneria, California-fuchsia, hummingbird flower, hummingbird trumpet Epilobium capense Epilobium × celakovskyanum Epilobium × chateri Epilobium chionanthum Epilobium chitralense Epilobium chlorifolium Epilobium ciliatum – fringed willowherb, American willowherb Epilobium clarkeanum Epilobium clavatum – talus willowherb, clavatefruit willowherb Epilobium cleistogamum – selfing willowherb Epilobium cockayneanum Epilobium colchicum Epilobium collinum Epilobium coloratum – purpleleaf willowherb Epilobium confertifolium Epilobium × confine Epilobium × confusilobum Epilobium confusum Epilobium conjungens Epilobium conspersum Epilobium × cornubiense Epilobium crassum Epilobium curtisiae Epilobium cylindricum Epilobium × dacicum Epilobium × dasycarpum Epilobium davuricum – Daurian willowherb Epilobium × decipiens Epilobium densiflorum – denseflower willowherb, dense spike-primrose, dense boisduvalia Epilobium densifolium Epilobium densum – downy willowherb, stiff spike-primrose Epilobium denticulatum Epilobium detznerianum Epilobium dodonaei Epilobium duriaei Epilobium elegans Epilobium × erroneum Epilobium × fallacinum Epilobium fangii Epilobium fastigiatoramosum Epilobium fauriei Epilobium × finitimum Epilobium fleischeri Epilobium × floridulum Epilobium forbesii Epilobium × fossicola Epilobium fragile Epilobium fugitivum Epilobium gemmascens Epilobium × gemmiferum Epilobium × gerstlaueri Epilobium glabellum – smooth spike-primrose Epilobium glaberrimum – glaucous willowherb Epilobium glaciale Epilobium × glanduligerum Epilobium glaucum Epilobium × goerzii Epilobium gouldii Epilobium gracilipes Epilobium × grenieri Epilobium griffithianum Epilobium gunnianum Epilobium × gutteanum Epilobium hallianum – glandular willowherb Epilobium × haussknechtianum Epilobium × haynaldianum Epilobium × hectori-leveilleanum Epilobium hectorii Epilobium × heterocaulon Epilobium hirsutum – great willowherb, great hairy willowherb, hairy willowherb, codlins-and-cream, apple-pie, cherry-pie Epilobium hirtigerum Epilobium hohuanense Epilobium hooglandii Epilobium hornemannii – Hornemann's willowherb Epilobium howellii – Yuba Pass willowherb, subalpine fireweed Epilobium × huteri Epilobium indicum Epilobium insulare Epilobium × interjectum Epilobium × intersitum Epilobium × jinshaense Epilobium karsteniae Epilobium × keredjense Epilobium kermodei Epilobium keysseri Epilobium kingdonii Epilobium × kitcheneri Epilobium komarovianum – bronzy willowherb Epilobium komarovii Epilobium korshinskyi Epilobium × krausei Epilobium lactiflorum – milkflower willowherb, whiteflower willowherb Epilobium ladakhianum Epilobium laestadii Epilobium × lamotteanum Epilobium lanceolatum – spear-leaved willowherb Epilobium × langeanum Epilobium × laschianum Epilobium latifolium Epilobium laxum Epilobium leiophyllum Epilobium leptocarpum – slenderfruit willowherb Epilobium leptophyllum – bog willowherb, linear-leaved willowherb Epilobium × limosum Epilobium lipschitzii Epilobium luteum – yellow willowherb Epilobium macropus Epilobium margaretiae Epilobium × marshallianum Epilobium matthewsii Epilobium maysillesii Epilobium melanocaulon Epilobium × mentiens Epilobium microphyllum Epilobium minutiflorum Epilobium minutum – chaparral willowherb, desert willowherb, smallflower willowherb Epilobium mirabile – Olympic Mountain willowherb Epilobium × montaniforme Epilobium montanum – broad-leaved willowherb Epilobium nanhualpinum Epilobium nankotaizanense – Nankotaizan willowherb Epilobium × neogradiense Epilobium nerterioides Epilobium nevadense – Nevada willowherb Epilobium nivale Epilobium nivium – Snow Mountain willowherb Epilobium × novae-civitatis Epilobium nummulariifolium Epilobium nutans Epilobium × nutantiflorum Epilobium obcordatum – rockfringe willowherb Epilobium × obscurescens Epilobium obscurum – dwarf willowherb, short-fruited willowherb Epilobium oreganum – Grants Pass willowherb, Oregon fireweed Epilobium oregonense – Oregon willowherb Epilobium × palatinum Epilobium pallidiflorum Epilobium pallidum – largeflower spike-primrose Epilobium palustre – marsh willowherb Epilobium pannosum Epilobium parviflorum – small-flowered willowherb, hoary willowherb Epilobium pedicellare Epilobium pedunculare – rockery willowherb Epilobium pengii Epilobium × percollinum Epilobium pernitens Epilobium perpusillum Epilobium × persicinum Epilobium petraeum Epilobium pictum Epilobium platystigmatosum Epilobium ponticum Epilobium porphyrium Epilobium × prionophylloides Epilobium prostratum Epilobium pseudorubescens Epilobium × pseudotrigonum Epilobium psilotum Epilobium pubens Epilobium puberulum Epilobium × pulchrum Epilobium purpuratum Epilobium × purpureum Epilobium pycnostachyum Epilobium pyrricholophum Epilobium ravenii – leafy willowherb, California willowherb Epilobium rechingeri Epilobium × reedii Epilobium rhynchospermum Epilobium rigidum – stiff willowherb, Siskiyou Mountains willowherb Epilobium × rivulare Epilobium × rivulicola Epilobium roseum – pale willowherb Epilobium rostratum Epilobium rotundifolium Epilobium royleanum Epilobium rubromarginatum Epilobium salignum Epilobium sarmentaceum Epilobium saximontanum – Rocky Mountain willowherb Epilobium × schmidtianum Epilobium × schulzeanum Epilobium semiamplexicaule Epilobium septentrionale – northern willowherb, Humboldt County fuchsia Epilobium × sericeum Epilobium sikkimense Epilobium × similatum Epilobium × simulatum Epilobium sinense Epilobium siskiyouense – Siskiyou willowherb, Siskiyou fireweed Epilobium smithii Epilobium speciosum Epilobium spitianum Epilobium staintonii Epilobium stereophyllum Epilobium stevenii Epilobium stracheyanum Epilobium subalgidum Epilobium subcoriaceum Epilobium subdentatum Epilobium suffruticosum – shrubby willowherb Epilobium × surreyanum Epilobium taiwanianum Epilobium tasmanicum Epilobium tetragonum – square-stemmed willowherb Epilobium thermophilum Epilobium × thuringiacum Epilobium tianschanicum Epilobium tibetanum Epilobium tonkinense Epilobium torreyi – Torrey's willowherb, brook spike-primrose Epilobium × treleaseanum Epilobium trichophyllum Epilobium tulinianum Epilobium turkestanicum Epilobium × udicola Epilobium × uechtritzianum Epilobium ulleungensis Epilobium vernicosum Epilobium vernonicum Epilobium verticillatum Epilobium × vicinum Epilobium wallichianum Epilobium × waterfallii Epilobium wattianum Epilobium williamsii Epilobium willisii Epilobium wilsonii Epilobium × winkleri Epilobium × wisconsinense – Wisconsin willowherb
Formerly placed here Stylidium tenellum (as E. tonkinense)
It is possible to distinguish between leaves of different Epilobium species using high-accuracy FT-IR method based on attenuated total reflection (ATR) without time-consuming preparation.Krajšek, S., Buh, P., Zega, A., Kreft, S. (2008). Identification of herbarium whole-leaf samples of Epilobium species by ATR-IR spectroscopy. Chemistry & Biodiversity, 5:310-317 http://onlinelibrary.wiley.com/doi/10.1002/cbdv.200890028/abstract;jsessionid=46F30B7C6B30DADFBD57A4789993E047.f01t02
Distribution and habitat Epilobium has a cosmopolitan distribution.
Conservation Epilobium vernonicumCheminal, A. 2024. Epilobium vernonicum. The IUCN Red List of Threatened Species 2024: e.T237663323A237931911. https://dx.doi.org/10.2305/IUCN.UK.2024-2.RLTS.T237663323A237931911.en. Accessed on 20 September 2026. and Epilobium psilotum are near threatened species.Rhazi, L., Grillas, P. & Rhazi, M. 2010. Epilobium psilotum. The IUCN Red List of Threatened Species 2010: e.T164213A5780578. https://dx.doi.org/10.2305/IUCN.UK.2010-2.RLTS.T164213A5780578.en. Accessed on 20 September 2026.
Footnotes
References