Titanopsis calcarea
| Light | Bright light to full sun; a sunny windowsill or open greenhouse |
|---|---|
| Water | Sparingly in autumn and spring; keep dry in the heat of summer and cold of winter |
| Soil | Very gritty, lean, alkaline-tolerant mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; USDA zones 9–11, tolerates a light brief frost if dry |
| Propagation | Seed; division of established clumps |
| Toxicity | Generally regarded as non-toxic to cats and dogs |
Titanopsis calcarea is the best-known member of the Titanopsis genus, a small clumping succulent from South Africa in the family Aizoaceae. It forms tight rosettes of blue-grey, spoon-shaped leaves whose tips are crusted with rough, wart-like tubercles that mimic the weathered limestone among which it grows — a camouflage so convincing it has earned the common name concrete leaf. In autumn and winter the plants open cheerful yellow-orange flowers that seem oversized for such a squat little plant.
Description
Titanopsis calcarea is a low, mat-forming succulent that slowly builds up into small clumps of rosettes. Each leaf is club- or spoon-shaped, broadest and truncated at the tip, and coloured a soft blue-grey to grey-green. The distinctive feature is the leaf tip: it is thickened and covered in a dense crust of raised, rounded tubercles or warts, often tinged rust, cream or bluish, giving the surface the pitted look of limestone rock.
This warty camouflage is the plant's defence — nestled among pale calcareous stones in habitat, a resting rosette is almost impossible to pick out. The daisy-like flowers appear from the centre of the rosettes, typically in autumn into early winter, opening in the afternoon sun in shades of golden yellow to orange, 1–2 cm across.
Distribution and habitat
The species is native to the arid interior of South Africa, particularly the Upper Karoo and Bushmanland of the Northern Cape, where it grows on flat, stony ground in limestone-rich (calcareous) soils — the origin of the epithet calcarea. It endures a harsh regime of intense sun, sparse rainfall and wide swings between hot days and cold nights, sheltering low among the rocks that it so closely resembles.
Cultivation
Titanopsis calcarea is one of the easier "living stone" type mesembs to grow, and more forgiving than the closely watched Lithops. The essentials are strong light and a very free-draining, lean mineral mix — extra grit, pumice or coarse sand, and it appreciates the alkaline conditions its name implies, so a little limestone or crushed shell in the mix suits it well.
Water is the main thing to get right. Grow it on the dry side and follow its natural rhythm: water in autumn and spring when it is in active growth, and keep it mostly dry through the peak heat of summer and the cold of winter. Overwatering, especially in a poorly draining pot, quickly causes rot. Give it the sunniest spot you can; in too little light the rosettes stretch, pale and lose their compact, rocky character. See Watering and Repotting for general technique.
Propagation
Seed is the primary method and germinates readily when sown on a gritty surface kept lightly moist and warm; sow thinly, as seedlings are tiny and slow at first. Established clumps can also be divided — lift a mature plant, tease apart rooted rosettes, and pot them separately, allowing any wounds to callus before watering. See Propagation — seed and Propagation — offsets for details.
Common problems
- Rot — the usual cause of loss, from watering during summer dormancy or winter cold, or from a mix that holds too much moisture.
- Etiolation — insufficient light makes the rosettes elongate and soften, losing the tight, warty, stone-like form.
- Pests — mealybugs can hide in the crowns and among the leaf tubercles; root mealybugs are worth checking for at repotting time. See Pests and diseases.
See also
- Titanopsis — the genus overview
- Lithops — another popular South African "living stone" mesemb
- Soil and potting mix · Watering · Propagation — seed · Propagation — offsets · Repotting