Spurge

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Spurge
Euphorbia cotinifolia ssp. cotinoides
Euphorbia cotinifolia ssp. cotinoides
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Malpighiales
Family: Euphorbiaceae
Subfamily: Euphorbioideae
Tribe: Euphorbieae
Subtribe: Euphorbiinae
Genus: Euphorbia
L.
Diversity
More than 2000 species worldwide
Species
See full list.

Spurges (genus Euphorbia) are a very large and diverse worldwide group of plants, belonging to the spurge family, or Euphorbiaceae.

Contents

[edit] Origin of the name

The common name spurge derives from the Middle English / Old French: espurge, to purge, due to the use of the plants sap as purgative.
The botanical name Euphorbia derives from the Greek Euphorbus, physician of king Juba II of Numidia (52-50 BC - 23 AD), in whose honour – or in allusion to his swollen belly – a certain plant he might have used, possibly Euphorbia resinifera, was named (Euphorbia regisjubae - King Juba's euphorbia - honors the king's contributions to natural history and his role in bringing the genus to notice). In 1753 Carolus Linnaeus assigned the name to the entire genus (Spec. Pl. (ed. 1): 450). Type species is Euphorbia antiquorum L..

[edit] Description

The plants are annual or perennial herbs, woody shrubs or trees with a caustic, poisonous milky sap (latex). The roots are fine or thick and fleshy or tuberous. Many species are more or less succulent, thorny or unarmed. The main stem and mostly also the side arms of the succulent species are thick and fleshy, 15-91 cm (6-36 inches) tall. The deciduous leaves are opposite, alternate or in whorls. In succulent species the leaves are mostly small and short-lived. The stipules are mostly small, partly transformed into spines or glands, or missing.

Like all members of the family Euphorbiaceae, all spurges have unisexual flowers. In Euphorbia these are greatly reduced and grouped into cyathia called pseudanthia. There are also (monoecious) species with male and female flowers on the same plant and those (dioecious) with male and female flowers occurring on different plants. It is not unusual for the central cyathia of a cyme to be purely male, and for lateral cyathia to carry both sexes. Sometimes young plants or those growing under unfavourable conditions are male only, and only produce female flowers in the cyathia with maturity or as growing conditions improve. The bracts are often leaf-like, sometimes brightly coloured and attractive, sometimes reduced to tiny scales. The fruits are three (rarely two) compartment capsules, sometimes fleshy but almost always ripening to a woody container that then splits open (explosively). The seeds are 4 angled, oval or spherical with or without a caruncle.

[edit] Xerophytes and succulents

In the genus Euphorbia succulence in the species has often evolved divergently and to differing degrees. Sometimes it is difficult to decide, and it is a question of interpretation, whether or not a species is really succulent or "only" xerophytic. In some cases, especially with geophytes, plants closely related to the succulents are normal herbs. About 850 species are succulent in the strictest sense. If one includes slightly succulent and xerophytic species, this figure rises to about 1000, representing about 45% of all Euphorbia species.

[edit] Latex

The latex (milky sap) of spurges acts as a deterrent for herbivores as well as a wound healer. Usually it is white, but in rare cases (e.g. E. abdelkuri ) yellow. As it is under pressure, it runs out from the slightest wound and congeals within a few minutes of contact with the air. Among the component parts are many di- or tri-terpen esters, which can vary in composition according to species and in some cases the variant may be typical of that species. The terpen ester composition determines if the latex is slightly or very caustic and irritating to the skin, and especially if in contact with mucous membranes (eyes, nose, mouth) can produce extremely painful inflammation. In experiments with animals it was found that the terpen ester resiniferatoxin had an irritating effect 10,000 to 100,000 times stronger than capsaicin, the "hot" substance found in chillies. Several terpen esters are also known to be carcinogenic.

Therefore handling spurges needs to be done with caution. Latex coming in contact with the skin should be washed off immediately and thoroughly. Partially or completely congealed latex is often no longer soluble in water, but can be removed with an emulsion (milk, hand-cream). With inflammation of a mucous membrane a doctor needs to be consulted. If cutting large succulent spurges in a greenhouse, it has been noticed that vapours from the latex spread and can cause severe irritation to the eyes and air passages several metres away. Caution is therefore required and for example ensure sufficient ventilation. Small children and domestic pets should never come into contact with spurges.

[edit] Distribution

The genus is primarily found in the tropical and subtropical regions of Africa and the Americas, but also in temperate zones worldwide. Succulent species are mostly originated from Africa, the Americas and Madagascar.

[edit] Uses

Several spurges are grown as garden plants, among them the poinsettia (Euphorbia pulcherrima) and the succulent Euphorbia trigona. E. pekinensis (Chinese: 大戟; pinyin: dàjǐ) is used in traditional Chinese medicine, where it is regarded as one of the 50 fundamental herbs. Several Euphorbia species are used as food plants by the larvae of some Lepidoptera (butterflies and moths), including the Giant Leopard Moth.

[edit] Taxonomy

Simplified diagram of relations in subtribe Euphorbiinae
Simplified diagram of relations in subtribe Euphorbiinae

[edit] Subtribe Euphorbiinae

According to recent DNA studies[citation needed] the so called satellite genera around the huge genus Euphorbia in subtribe Euphorbiinae nest deep within Euphorbia. Consequently these satellites, namely the never generally accepted genus Chamaesyce as well as the smaller genera Elaeophorbia, Endadenium, Monadenium, Synadenium and Pedilanthus were transferred to Euphorbia by Steinmann & Porter (2002), Steinmann (2003) and Bruyns & al. (2006). Besides the yet remaining satellite genus Cubanthus which is closely related to Pedilanthus and hence will very likely be transferred to Euphorbia as well in the near future, the entire subtribe Euphorbiinae now consist of genus Euphorbia.

[edit] Selected Euphorbia species

See List of Euphorbia species for complete list.

[edit] Subgenera

The genus Euphorbia is one of the largest and most complex genera of flowering plants and several botanists have made unsuccessfully attempts to subdivide the genus into numerous smaller genera. Now according to recent DNA studies[citation needed] Euphorbia can be divided into 4 subgenera, each containing several not yet sufficiently studied sections and groups.

  • Esula

Euphorbia amygdaloides

Euphorbia cyparissias

Euphorbia esula

Euphorbia myrsinites
  • Rhizanthium

Euphorbia ferox

Euphorbia flanaganii

Euphorbia meloformis ssp. valida

Euphorbia hamata

Euphorbia obesa ssp. symmetrica

Euphorbia polycephala
  • Chamaesyce

Euphorbia celastroides

Euphorbia hyssopifolia

Euphorbia rivae

Euphorbia heterophylla

Euphorbia leucocephala

Euphorbia pulcherrima

Euphorbia radians var. radians

Euphorbia californica var. californica

Euphorbia guiengola

Euphorbia xanti

Euphorbia abdelkuri

Euphorbia actinoclada

Euphorbia aeruginosa

Euphorbia confinalis ssp. rhodesica

Euphorbia graciliramea

Euphorbia piscidermis

Euphorbia resinifera

Euphorbia sepulta

Euphorbia alfredii

Euphorbia lophogona

Euphorbia milii var. vulcanii

Euphorbia primulifolia var. primulifolia

Euphorbia attastoma var. attastoma

Euphorbia lupulina

[edit] Literature

  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 1 Strawberry Press, Mill Valley, California, USA 1983. ISBN 0-912647-00-0
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 2 Strawberry Press, Mill Valley, California, USA 1984. ISBN 0-912647-01-9
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 3 Strawberry Press, Mill Valley, California, USA 1985. ISBN 0-912647-02-7
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 4 Strawberry Press, Mill Valley, California, USA 1987. ISBN 0-912647-04-3
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 5 Strawberry Press, Mill Valley, California, USA 1988. ISBN 0-912647-05-1
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 6 Strawberry Press, Mill Valley, California, USA 1989. ISBN 0-912647-06-X
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 7 Strawberry Press, Mill Valley, California, USA 1991. ISBN 0-912647-08-6
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 8 Strawberry Press, Mill Valley, California, USA 1992. ISBN 0-912647-10-8
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 9 Strawberry Press, Mill Valley, California, USA 1994. ISBN 0-912647-11-6
  • Schwartz, Herman (Ed.): The Euphorbia Journal Vol. 10 Strawberry Press, Mill Valley, California, USA 1996.
  • Eggli, Urs (Ed.): Sukkulentenlexikon Band 2: Zweikeimblättrige Pflanzen (Dicotyledonen) Eugen Ulmer Verlag, Germany 2002. ISBN 3-8001-3915-4
  • Singh, Meena: Succulent Euphorbiaceae of India New Delhi, India 1994 (Mrs. Meena Singh, A-162 Sector 40, NOIDA - 201303, India)
  • Buddensiek, Volker Succulent Euphorbia plus Volker Buddensiek Verlag 2005, CD-ROM. ISBN 3-934396-03-8
  • Noltee, Frans: Succulents in the wild and in cultivation, Part 2 Euphorbia to Juttadinteria 2001, CD-ROM. ISBN 90-76774-05-6
  • Turner, Roger: Euphorbias - A Gardeners' Guide, Batsford, England, 1995. ISBN 0 7134 7071 2, pbk ed. 1998, 0 7134 8384 9.
  • Carter, Susan: New Succulent Spiny Euphorbias from East Africa, 1982. ISBN 1-878762-72-9
  • Carter, Susan & Smith, A.L.: Flora of Tropical East Africa, Euphorbiaceae 1988. ISBN 90-6191-338-1
  • Carter, Susan & Eggli,Urs: The CITES Checklist of Succulent Euphorbia Taxa (Euphorbiaceae) 1997. ISBN 3-89624-609-7
  • Pritchard, Albert: Introduction to the Euphorbiaceae 2003. ISBN 88-900511-3-2

[edit] References

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