Crown of thorns (Euphorbia)

Euphorbia milii belongs to the genus Euphorbia in the family Euphorbiaceae. It is native to Madagascar, and one of its English common names is crown of thorns.

This page goes only as far as the genus (Euphorbia spp.). Our plant came from a garden shop and its variety is uncertain: it may include Euphorbia milii, or it may be a hybrid with Euphorbia geroldii.

The bright red parts are not petals but bracts. Each crown of thorns cyathium sits above 2 kidney-shaped to round bracts, usually bright red, and pink, white or yellow in some cultivars; the glands in the middle are yellowish red. According to the Flora of China, the stems are densely spiny, and the spines are modified stipules.

Euphorbia plants contain latex throughout, usually white. North Carolina State University Extension recommends wearing gloves when handling crown of thorns to prevent skin and eye irritation from the sap. It is toxic if eaten, so keep it out of reach of small children and pets.

The full structure of the cyathium is described in the note The crown of thorns my mum brought home.