Oxalis convexula, convex-leaved wood sorrel, cushion sorrel, 15 seeds 2023
Easily recognised for its well-developed above-ground stem and rounded appearance, Oxalis convexula is one of the more distinct members of the Oxalis genus. The plant has been described as looking like a small lollipop standing above the ground in the Renosterveld.
Also known as the convex-leaved wood sorrel, this species grows on shale-derived soils from Ceres to Riversdale. Its salmon pink and yellow-tubed blooms are produced from June through to September. The species name means ‘with a rounded shape’, referring to the shape of the plant.
Origin and Habitat: Western cape (Karoo and Little Karoo) and Lesotho.
Description: The Cussion Sorrel is a low growing, stemless or short-stemmed, perennial geophytic herb that grows from a fairly deeply positioned underground bulb, glabrous throughout. The the leaves comprise three roundish convex and succulent leaflets. The rosy-salmon flowers with a yellow throat appear in autumn and winter and may extend to spring. The plant reaches heights of up to 15 cm.
Stem: Shortly subterraneous, then standing out from 7-12 cm long, round, purple, smooth, without scales, the thickness of a pigeon's quill or thicker, wholly procumbent, branched, brittle, with a central tough fibril, thickened at the tip, and from this terminated by a very close and elegant umbel of leaves and flowers.
Bulb: Deeply positioned, oval tapering at both ends, the size of a hazel nut to twice that bigness, blackish brown, smooth.
Leaves: Very numerous, spreading every way, trifoliolate. Leaflets almost circular, toothless or with just a hint of a shallow notch at the tip of especially the middle leaflet, thick and fleshy, sub-convex or flat, punctate on both faces, veinless, paler underneath, 6-8 mm wide and long.
Inflorescences: Flowers grow solitary on fleshy stalks longer than the leaves, bibracteolate above the middle. Petioles 2.5-7.5 cm long. Bracteoles alternate or opposite.
Flowers: Salmon pink to cerise, yellow inside the corolla tube. Calyx 4-6 mm long. Sepals lanceolate, obtuse, mostly with one or two apical calli, ciliolate, less than half to 4 times shorter than the corolla. Corolla 16-24 mm long, with yellowish claw and rosy, white, or pale violet petals that form a funnel-shaped tube, spreading widely at the mouth in five broad lobes with angular to rounded tips. Claws of the petals equalling the lamina or shorter. Fine, slightly darker lines radiate from the centre along the petal surfaces. Styles middling filaments pilose or glandular.
Blooming season: Late autumn, winter and early spring.
Cultivation and Propagation: Oxalis convexula is suited for alpine house. Need a dry rest in summer, watering from November
Propagation: Division of resting tubers. Seed in spring, germination 1-3 months at about 18-21°C. The plants also form multiple small bulbils clustered about the axis of the flower stems. These are deposited on the ground below the plants and they produce new plantlets either in spring or in the autumn. If not destroyed, they produce within several months a new crop of flowering specimens.