Argyroderma delaetii
| Light | Very bright light, ideally with some direct sun; tolerates gentle morning sun outdoors |
|---|---|
| Water | Very sparingly, and only in its growing season (autumn to spring); keep bone-dry through summer dormancy |
| Soil | Extremely gritty, sharp-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep frost-free; USDA zones 9b–11, ideally kept dry and cool in winter |
| Propagation | Seed (primary); division of older clumps |
| Toxicity | Not known to be toxic to cats or dogs |
Argyroderma delaetii is a small, stemless succulent from the winter-rainfall region of South Africa that forms smooth, egg- to sphere-shaped bodies of a distinctive chalky grey-green. Each plant consists of a pair of thick, fused leaves split by a central fissure, and in season it produces surprisingly large, showy flowers in shades of magenta or yellow, and less commonly white. It belongs to the Argyroderma genus, whose name — from the Greek for "silver skin" — refers to the pale, silvery sheen of these plants.
Description
Argyroderma delaetii grows as a compact, near-stemless plant made up of one or two pairs of very fleshy leaves fused into a smooth, rounded body 2–4 cm across. The leaf pair is united for most of its length and separated only by a narrow fissure across the top, giving the plant its characteristic "split egg" or "living stone" look. The surface is smooth and firm, with a chalky, silvery grey-green colour that helps it blend into the pale quartz gravel of its habitat.
Flowers emerge from the fissure, one per body, and are large relative to the plant — daisy-like and many-petalled, most often in vivid magenta or clear yellow, and less commonly white, depending on the individual. Each plant renews itself by producing a fresh pair of leaves from within the fissure, drawing on the old pair, which shrivels as the new growth swells. Over years a plant may slowly form a small clump of a few heads.
Distribution and habitat
The species is native to the Knersvlakte, an arid quartz-gravel region in the Western Cape of South Africa. This is a winter-rainfall area: plants receive most of their moisture in the cooler months and endure a hot, dry summer. They grow nestled among white quartz pebbles, where their pale bodies are well camouflaged, rooted in mineral-rich, extremely free-draining ground with very little organic matter.
Understanding this habitat is the key to growing the plant, because its water needs run on a winter-growth, summer-rest cycle that is the reverse of many familiar succulents.
Cultivation
Argyroderma delaetii is prized by mesemb enthusiasts but has a reputation for being unforgiving of watering mistakes — overwatering, or watering at the wrong time of year, is the usual cause of loss. Grow it in a very gritty, almost entirely mineral mix in a pot deep enough for its roots, and give it the brightest light you can, with good airflow.
Follow its natural rhythm: water sparingly through the cooler growing months (roughly autumn into spring), always letting the mix dry out fully between drinks, and keep the plant essentially dry through the heat of summer while it rests. A plant that plumps up its new leaf pair and gradually absorbs the old one is being watered correctly; splitting, bloating or a soft, translucent body is a sign of too much water. See Watering and Repotting for general technique.
Propagation
Seed is the primary and most reliable method. The fine seed is sown onto a mineral surface and kept lightly moist and warm until germination, after which seedlings are grown on very cautiously, as they are prone to rot if kept too wet. Established plants that have formed a clump of several heads can also be divided carefully when repotting. See Propagation - seed for a full walkthrough, and Propagation - offsets for handling divisions of older clumps.
Common problems
- Rot — the most common killer, almost always from overwatering or from watering during summer dormancy; the body softens and collapses.
- Splitting or bloating — too much water, especially while the old leaf pair is still being absorbed, leaves the plant swollen and prone to cracking.
- Etiolation — insufficient light makes the body elongate and lose its tight, rounded shape and silvery colour.
- Pests — mealybugs (white fluff around the fissure and roots) and root mealybugs are the usual culprits; see Pests and diseases.
See also
- Argyroderma — the genus overview
- Soil and potting mix · Watering · Propagation - seed · Repotting · Pests and diseases