Epilobium

Epilobium
Epilobium hirsutum (great willowherb)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Myrtales
Family: Onagraceae
Subfamily: Onagroideae
Tribe: Epilobieae
Genus: Epilobium
L.
Type species
Epilobium hirsutum L.
Species

192, see here

Synonyms
  • Boisduvalia Spach
  • Chamaenerion Ség.
  • Chamerion (Raf.) Raf. ex Holub
  • Cordylophorum Rydb.
  • Cratericarpium Spach
  • Crossostigma Spach
  • Epilobiopsis Speg. ex H.Lév.
  • Pyrogennema Lunell
  • Zauschneria C.Presl

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.

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

Ripe capsule of Epilobium canum (zauschneria) releasing seed

Epilobium are mostly herbaceous plants, either annual or perennial; a few are subshrubs. The leaves are opposite or rarely whorled,: 354  simple and ovate to lanceolate in shape. The flowers are actinomorphic (radially symmetrical) with four petals that may be notched. 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. The type species is Epilobium hirsutum L.

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 brachycarpum (tall willowherb)
Epilobium canum (zauschneria)
Epilobium alpestre
Top left: Epilobium alsinifolium (chickweed willowherb)
Bottom left: Epilobium anagallidifolium (alpine willowherb)
Center: Epilobium tetragonum (square-stemmed willowherb)
Epilobium billardierianum
Left: Epilobium roseum (pale willowherb)
Right: Epilobium obscurum (dwarf willowherb)
Epilobium parviflorum (small-flowered willowherb)
Chamaenerion fleischeri

Formerly placed here

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.

Distribution and habitat

Epilobium has a cosmopolitan distribution.

Conservation

Epilobium vernonicum and Epilobium psilotum are near threatened species.

Footnotes

  1. 1 2 Epilobium L. (n.d.). International Plant Names Index. Retrieved September 20, 2026, from https://www.ipni.org/n/30000954-2
  2. ↑ "Smithsonian National Museum of Natural history: Epilobium". Retrieved 22 February 2017.
  3. ↑ Bleeker et al. (2007)
  4. ↑ "willow-herb". Oxford English Dictionary (online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  5. 1 2 Stace, C. A. (2010). New Flora of the British Isles (Third ed.). Cambridge, U.K.: Cambridge University Press. ISBN 9780521707725.
  6. ↑ Webb, D.A., Parnell, J. and Doogue, D. 1996. An Irish Flora. Dundaldan Press (W. Tempest) Ltd, Dundalk. ISBN 0-85221-131-7
  7. ↑ "Smithsonian Onagraceae website". Retrieved 22 February 2017.
  8. ↑ Sennikov, Alexander N. (2011). "Chamerion or Chamaenerion (Onagraceae)? The old story in new words". Taxon. 60 (5): 1485–1488. doi:10.1002/tax.605028. JSTOR 41317556.
  9. 1 2 3 "Epilobium Dill. ex L." Plants of the World Online. Kew Science. Retrieved 2025-10-06.
  10. ↑ 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
  11. ↑ "Definition of EPILOBIUM". www.merriam-webster.com. Retrieved 30 August 2021.
  12. ↑ 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
  13. ↑ Cheminal, 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.
  14. ↑ 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.

References