Euphorbia inconstantia

Origin

Euphorbia inconstantia R.A.Dyer is endemic to a very small area of the Sekhukhuneland region of Limpopo, South Africa, with the type locality on the mafic and ultramafic hills near Steelpoort and Burgersfort (Africa). It was described by the South African botanist Robert Allen Dyer in the twentieth century from material collected on chromite-bearing serpentine outcrops, and it is one of the most range-restricted Euphorbias of the region. The species is listed as rare in South African Red Data assessments because of its narrow endemic distribution and the mining pressure on its habitat.

Habitat

In its natural environment, this species is a specialist of the Sekhukhuneland mountain bushveld on ultramafic substrates, where it grows in shallow pockets of gritty mineral soil over chromite-bearing serpentine and pyroxenite rock at altitudes around 800–1200 meters above sea level. Rainfall arrives in summer under a strongly seasonal climate, with cool dry winters. Plants perch in fully exposed positions and produce their deciduous branches after the summer rains have set in.

Description

Euphorbia inconstantia is a small, low-growing, deciduous South African Euphorbia whose combination of a stout underground tuber and slender, wiry branch rosettes makes it one of the most distinctive miniatures of the Sekhukhuneland flora.

Caudex & Stem: Below ground sits a thick, tuberous main stem that functions as the perennial storage organ. From its apex a rosette of slender, decumbent, segmented branches is produced each growing season; these branches die back and abscise at the end of the rains, leaving the tuber bare through winter.

Roots: A coarse, woody taproot descends from the tuber into the rocky serpentine subsoil, with finer laterals that exploit the brief moist season.

Spines & Stipules: The branch segments carry paired short stipular spines at each tubercle, forming neat horn-like pairs along the ribs. The species name, inconstantia, refers to the variability of these spine pairs in length and spacing between populations.

Flowers: Yellow-green cyathia are produced at the branch tips in the warm wet months, the characteristic cup-shaped true flowers of the genus, small and tidy against the dark green segments.

Cultivation: Grow in a deep mineral mix that keeps the tuber partially exposed for display, water generously while branches are present, and withhold water almost completely once the branches yellow and drop. Bright light and good air movement are essential, and the plant is frost-tender.