Euphorbia heterochroma, sometimes known as the African cathedral plant, is a species of flowering plant in the family Euphorbiaceae native to eastern Africa. It is a succulent shrub with a long history of use in East African traditional medicine.
The species was first described by the German botanist Ferdinand Albin Pax in 1895, based on specimens collected in Tanzania. The specific epithet heterochroma is derived from the Greek words heteros (different) and chroma (color), referring to the variable coloration of the plantâÂÂs stems and floral parts.
Two subspecies are recognized:
Euphorbia heterochroma subsp. heterochroma â the autonym subspecies.
Euphorbia heterochroma subsp. tsavoensis <small>S.Carter</small> â described by Susan Carter in 1987; distinguished by its smaller stature and more compact growth form, endemic to the Tsavo region of Kenya.
Heterotypic synonyms include:
Euphorbia heterochroma var. mitis <small>(Pax) N.E.Br.</small>
Euphorbia impervia <small>A.Berger</small>
Euphorbia mitis <small>Pax</small>
Euphorbia stuhlmannii <small>Schweinf. ex Volkens</small> (nom. illeg.)
Some specimens previously identified as E. heterochroma in southern Africa have since been reclassified as Euphorbia griseola subsp. griseola.
Euphorbia heterochroma is a straggly, succulent shrub with erect or decumbent branches that root where they touch the ground. It typically reaches up to in height, with moderate branching above.
The branches are 4-angled, occasionally 5-angled, measuring approximately in thickness. The angles are straight to shallowly undulate, with a green coloration that typically displays regular darker patches along the angles. The spineâÂÂshields are elongated, reaching up to above the spines, and may form a continuous horny margin along the angles. The spines are 1âÂÂ6 mm long, occasionally absent, with vestigial prickles.
The leaves are small and deltoid, approximately , with very obscurely toothed margins. The inflorescence consists of solitary, 1-forked cymes with stout peduncles and cymeâÂÂbranches 2âÂÂ3 mm long, appearing yellow or red. The cyathia (cupâÂÂlike structures containing the flowers) are approximately with cupâÂÂshaped involucres. The glands are transversely oblong, about , and contiguous. The male flowers feature fanâÂÂshaped, deeply laciniate bracteoles and stamens 3.8 mm long, while the female flower has styles 1.8 mm long joined at the base with rugose apices.
The fruit is a sharply 3âÂÂlobed capsule, approximately , exserted on a reflexed pedicel about 5 mm long. The seeds are ovoid, approximately , grey, and shallowly tuberculate.
Euphorbia heterochroma is native to Kenya and northeastern Tanzania. It grows in stony, sandy soils within Acacia and Commiphora thickets, as well as on rocky outcrops with deciduous thickets. In its native range it occurs at elevations between above sea level.
The flowers of Euphorbia heterochroma are visited by bees, similar to other succulent Euphorbia species.
Euphorbia heterochroma has a prominent place in East African traditional medicine, with various applications documented across Kenya, Uganda, and Tanzania:
A latex infusion or root decoction is taken to treat venereal diseases.
In Uganda, latex mixed with clay is applied to the skin or in incisions to treat syphilis.
In Kenya, an infusion of the latex or roasted stems is taken to treat fever, diarrhea, cough, tuberculosis, and pneumonia.
A leaf decoction is taken to treat stomachâÂÂache.
In Uganda, latex is applied to incisions to treat pyomyositis (a bacterial infection of skeletal muscle).
Latex is used as nose drops to treat migraine and insanity.
For veterinary use in Kenya, a root or stem infusion is given to camels to treat persistent cough and hemorrhagic septicaemia.
The latex is highly caustic and must be handled with care, as it can cause skin and eye irritation.
The species is occasionally cultivated as an ornamental plant in gardens and as a houseplant, valued for its distinctive succulent form. Like all succulent Euphorbia species, its trade is regulated under CITES Appendix II.
While no formal conservation assessment is currently published for Euphorbia heterochroma, its distribution within East Africa and occurrence in protected areas suggest it faces no immediate threat of extinction. However, as a succulent species, it is subject to CITES Appendix II regulations to ensure sustainable trade.
Carter, S. (2008). "Euphorbia in Tanzania". Euphorbia World 4(2): 5âÂÂ9.
Govaerts, R., Frodin, D.G. & RadcliffeâÂÂSmith, A. (2000). World Checklist and Bibliography of Euphorbiaceae (and Pandaceae) 1âÂÂ4: 1âÂÂ1622. The Board of Trustees of the Royal Botanic Gardens, Kew.