Euphorbia corniculata

Origin

Euphorbia corniculata R.A.Dyer is endemic to a small area of the arid interior of the Western and Northern Cape of South Africa, with the type locality in the Tanqua and northern Ceres Karoo (Africa). It was described in the twentieth century by Robert Allen Dyer from material collected on stony plains of the interior plateau, and it is one of the more interesting little spiny Euphorbias of the South African arid zone. Wild populations are stable across their range but the species remains uncommon in general cultivation.

Habitat

In its natural environment, this species is a specialist of the arid Tanqua Karoo and northern Ceres Karoo, where it grows in flat, stony mineral soils derived from weathered shale and mudstone at altitudes around 600–1100 meters above sea level. Rainfall is low and almost entirely confined to the cool winter months, with long, hot, dry summers. Plants sit in fully exposed positions and produce their leafy, flowering branches in the cool months, retreating to the main stem as the dry season sets in.

Description

Euphorbia corniculata is a small, spiny South African Euphorbia whose paired, horn-like stipular spines along slender branches give the species its name and make it one of the more sculptural miniatures of the Karroid flora.

Stems & Caudex: The plant forms a low, much-branched, semi-succulent shrub 20–40 cm tall, with cylindrical, jointed, dull green stems that can thicken with age into a small, somewhat woody basal caudex.

Roots: A coarse, somewhat tuberous root system anchors the plant into the stony Karoo substrate and helps it survive the long dry summer by storing limited moisture.

Spines & Stipules: The stems carry paired, slender, dark stipular spines at each tubercle, forming neat, evenly spaced horn-like pairs along the ribs. The species name, corniculata, refers to these small horn-like spine pairs, which are diagnostic of the species and distinguish it from related Karoo Euphorbias.

Leaves: Leaves are produced at the stem tips in the cool months, small, narrowly obovate, and often flushed with red or purple in bright light, then shed as the dry summer sets in.

Flowers: The true flowers are the genus-typical yellow-green cyathia, produced in small clusters at the branch tips in late winter to early spring, modest in size but ornamental against the dark stem.

Cultivation: Grow in a sharply drained, mineral-rich mix under bright light and good air movement. Water moderately during the cool growing months and withhold water almost completely in the hot dry summer, when the plant is fully deciduous. The species is frost-tender and resents disturbance of its root system.