Epilobium

Epilobium
Great Willowherb (Epilobium hirsutum)
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Eudicotyledoneae
Subclass: Rosidae
Order: Myrtales
Family: Onagraceae
Genus: Epilobium
L.
Species

160-200, see text
Synonyms

Boisduvalia
Chamaenerion
Chamerion (but see text)
Pyrogennema
Zauschneria

Epilobium is a genus in the family Onagraceae, containing about 160-200 species of flowering plants with a worldwide distribution. They are generally abundant in the subarctic, temperate and subantarctic regions, whereas in the subtropics and tropics they are restricted to the cool montane biomes, such as the New Guinea Highlands where they are plentiful.

The taxonomy of the genus has varied between different botanists, but the modern trend is to include the previously recognised genera Boisduvalia, Chamaenerion, Chamerion, Pyrogennema and Zauschneria within Epilobium. Chamerion might be distinct however[1], as advocated for example by Peter H. Raven who has extensively studied the willowherbs and does on the other hand merge the other segregate genera into Epilobium. Fringed Willowherb (E. ciliatum) is suspected to be a cryptic species complex; apparently these plants also commonly hybridize with their congeners[2].

Most species are known by the common name willowherbs; in particular those that were once separated in Boisduvalia are called spike-primroses or boisduvalias. Yet other species, namely ones that are placed in the Chamerion group, are also known as "fireweeds".

Contents

Description and ecology

They are mostly herbaceous plants, either annual or perennial; a few are subshrubs. The leaves are mostly opposite or whorled, alternate in a few species, simple, and ovate to lanceolate in shape. The flowers have four petals. These are usually smallish and pink in most species, but red, orange or yellow in a few, and large and bright magenta in the Chamerion group. 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.

Willowherbs are typically very quick to carpet large swathes of ground and may form key or even dominant species of local ecosystem. In and around the United Kingdom for example, Rosebay Willowherb (E. angustifolium) is widely found in mesotrophic grassland dominated by False Oat-grass (Arrhenatherum elatius), Cock's-foot (Dactylis glomerata) and Red Festuce (Festuca rubra), while Great Willowherb (Epilobium hirsutum) is found in mesotrophic grassland with abundant False Oat-grass, Cock's-foot and Stinging Nettle (Urtica dioica). These two willowherb species are also seen to dominate open habitat early in ecological succession, to the virtual exclusion of other plant life. Broad-leaved Willowherb (Epilobium montanum) is found characteristically though not abundantly in the mesotrophic grasslands rich in False Oat-grass, Meadowsweet (Filipendula ulmaria), and sometimes the otherwise rare Greek Valerian (Polemonium caeruleum), which are peculiar to the Pennines. Most willowherbs will not tolerate shade trees well and thus are limited to comparatively freshly disturbed patches, yielding to other plants as the years pass by. Consequently, though the genus contains many pioneer plants, rather few of them are invasive weeds of major importance.

Epilobium species are used as food plants by the caterpillars of certain Lepidoptera species, including:
Geometridae

Noctuidae

Sphingidae

Use by humans

Many of the small willowherb species are nuisance weeds in gardens. Though few are regularly used as ornamental plants, most people find the larger willowherbs to give a pleasing aspect to ruderal locales. One of the most frequently recognized members of the genus is the circumboreal Fireweed (E. angustifolium), known as Rosebay Willowherb in the United Kingdom. It rapidly colonizes burnt ground; during the bombing of London in World War II many of the derelict bomb sites were soon covered with these plants, bringing a splash of colour to what was otherwise a very grim scene. Epilobium angustifolium is the floral emblem of Yukon territory in Canada, Hedmark county in Norway (where the plant is called geitrams) and of the Southern Ostrobothnia region of Finland.

Fireweed is used as a sweetener in northwestern North America; it is put in candies, jellies ice cream, syrup and other treats, as well as in sxusem ("Indian ice-cream"). In the latter months of summer its flowers yield pollen and copious nectar which gives a rich spicy honey. Its young leaves, roots and shoots are edible (if somewhat bitter) and rich in provitamin A and vitamin C; the Dena’ina found them also useful as food supplement to keep their dogs healthy and credit the sap of the species' stem, applied to wounds, with antiinflammatory properties. Small-flowered Willowherb (E. parviflorum) is held to improve urogenital functions in European folk medicine

Several eminent scientists have done research on these plants: Heinrich Carl Haussknecht in the late 19th century and Peter H. Raven about a century later have researched phylogeny, systematics and taxonomy of willowherbs extensively. Peter Michaelis' studies of this genus paved the way for understanding of extranuclear inheritance in plants.

Species

The National Museum of Natural History recognizes an intermediate number of about 175 species in 10 sections, including two sections of Chamerion which they consider distinct[1]. Other sources may list one or two dozen species more or less:

Section Boisduvalia

Section Cordylophorum

Subsection Nuttalia
Subsection Petrolobium

Section Crossostigma

Section Epilobiopsis

Section Macrocarpa

Section Xerolobium

Section Zauschneria

Section Epilobium

Chamerion group

Section Chamerion

Section Rosmarinifolium

Formerly placed here

Footnotes

  1. ^ a b Wagner & Hoch [2009a,b]
  2. ^ Bleeker et al. (2007)

References