When flowering Gerold’s spurge is similar to the thorny Euphorbia milii (Crown of Thorns)
and is known as the Thornless Crown of Thorns.
They are rounded, semi-succulent much-branched shrubs up to 1 (2) m high.
The woody branches have no spines.
The leaves are alternate in a roughly spiral pattern.
The base of the dark green ovate leaves tapers to a short petiole.
The 2 mm long stipules at the petiole base have a fringed edge.
The shiny, succulent blades are up to 8 cm long and have a very wavy edge.
They have a shiny surface and a narrow red line around the margin.
The branched axillary inflorescences, on peduncles are near the ends of the branches.
Each cyathium has a red bell-shaped involucre with 2 large bright red bracts at the base.
The cyathia are 2 mm across and the round to kidney-shaped bracts are around 2.6 cm.
The shrubs flower for most of the year.
The rim of the involucre has 5 large pale yellowish elliptic nectar glands with slightly depressed centres.
Inside the involucre are about 5 male flowers around a single female one.
The male flowers consist of a stamen with a basifixed bi-lobed anther on a thick filament.
The articulated stamens fall off when their pollen has been released.
Each stamen is surrounded by bracteoles with a hairy upper section.
The female flower has a 3-chambered ovary on a short pedicel.
The bases of the 3 bifid styles are fused for over half their length.
Each style branch has a globular stigma.
The fruit are pale, slightly lobed capsules 3 mm across.
Euphorbia ‘Cotton Candy’, a 1.5 m high hybrid of Euphorbia geroldi and E. robivelonae has bright pink flowers.