Pleiospilos
Pleiospilos is a small genus of stemless, clump-forming succulents in the ice plant family Aizoaceae, native to the arid interior of South Africa. Each plant carries just a few very fat, dome-shaped leaves, greyish-green and finely dotted with darker glands, that mimic the split, weathered granite among which the plants grow — earning them common names such as split rock, living granite and mimicry plant. In autumn to spring they surprise growers with large, glossy, coconut-scented flowers that seem far too big for the modest bodies that produce them.
Description
Pleiospilos are true mesembs: low, essentially stemless plants that sit flush with the soil surface. A mature head consists of only one or two pairs of leaves at a time, each leaf thick, hemispherical or wedge-shaped, and often nearly as wide as it is long. The surface is smooth and matte, coloured a soft grey-green to brownish-grey and speckled all over with tiny raised dots — the glandular flecks that give the genus its scientific name (from the Greek for "full of spots") and its uncanny resemblance to chips of granite.
The plants renew themselves by producing a fresh pair of leaves from between the old pair each growing season, drawing the old leaves down as they shrivel. Flowers arise from the cleft between the leaves and are large and daisy-like — yellow, orange or, in some species, with a paler centre — and many carry a distinct coconut-like scent. Older clumps slowly build into small mounds of several heads.
Distribution
The genus is confined to South Africa, chiefly the arid Karoo and adjoining semi-desert regions of the Eastern and Western Cape. Plants grow in open, sun-baked ground among quartz gravel, shale and granite, where their dotted, stony bodies are remarkably hard to spot until they flower. Rainfall in these habitats is low and often seasonal, and the plants endure long dry spells by shrinking into the surrounding rock and grit.
Notable species
- Pleiospilos nelii — the classic split rock, forming a near-spherical pair of fat grey-green leaves; the most widely grown species and the source of the popular purplish-bronze cultivar Royal Flush.
- Pleiospilos compactus — larger and more elongated, with wedge-shaped, angular leaves and orange to yellow flowers.
- Pleiospilos bolusii — with broad, blunt, chin-like leaves heavily dotted with dark glands, closely resembling a piece of weathered stone.
Cultivation
Pleiospilos are prized by mesemb enthusiasts and, with the right watering rhythm, are quite forgiving — but they are unforgiving of kindness at the wrong time of year. Grow them in a very open, mostly mineral mix with plenty of coarse grit or pumice, in a deep pot that suits their long taproot, and give them the brightest light you can. Full sun keeps the bodies compact and firmly coloured; too little light makes them bloat, pale and split.
The key to success is respecting their growth cycle. These are cool-season growers that are largely dormant through the heat of high summer. Water carefully in autumn and spring when they are in active growth and forming new leaves, and keep them almost completely dry in summer and through cold winter spells. The most common mistake is watering while a new leaf pair is emerging: the plant should be reabsorbing the old leaves, and extra water at this stage causes it to stack multiple pairs, bloat and rot. Let the old leaves wither to paper naturally. See Watering and Repotting for general technique.
Most Pleiospilos are raised from seed, which germinates readily on a gritty, mineral surface kept lightly moist and warm; seedlings are slow but steady. Established clumps can sometimes be divided, and offsets separated with a piece of root, though the genus is not a prolific offsetter. See Propagation — seed and Propagation — offsets for details.
Cultivars and hobby notes
Selection within the genus is modest compared with many succulents, but P. nelii has produced the well-known Royal Flush line, whose leaves flush a striking purple-bronze rather than the usual grey-green, especially under strong light and cool nights. Growers value Pleiospilos as showpiece mimicry plants alongside other stone-mimics such as Lithops and Titanopsis, and the outsized, fragrant flowers make them a favourite among mesemb collectors. Colour intensity, compactness and flower size all respond strongly to light and to a disciplined dry rest.
See also
- Aizoaceae — the ice plant family
- Pleiospilos nelii · Pleiospilos compactus · Pleiospilos bolusii
- Soil and potting mix · Watering · Repotting · Propagation — seed · Propagation — offsets
- Pests and diseases