Turbinicarpus polaskii
| Light | Bright light with light shade from harsh midday sun |
|---|---|
| Water | Very sparingly; dry out completely between waterings, keep bone-dry in winter |
| Soil | Gritty, mostly mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; hardy to a cool, dry winter rest |
| Propagation | Seed |
| Toxicity | Non-toxic to cats and dogs |
Turbinicarpus polaskii is a small, soft-bodied cactus with strongly reduced spination and white flowers, native to the arid limestone country of north-central Mexico (eastern San Luis Potosí). It is usually treated as a member of the variable Turbinicarpus schmiedickeanus complex, and its taxonomic rank has shifted repeatedly between species, subspecies and synonym as botanists have wrestled with just how finely to divide this group. Whatever name it carries on a given label, it is prized by collectors for its miniature size, gently corky body and soft, almost harmless spines.
Description
Turbinicarpus polaskii is a diminutive, mostly solitary plant with a small, soft, tuberculate body seldom more than a few centimetres across. As with much of the genus, the plant sits low with a broad taproot below and only the flattened crown showing above the soil line, so that in habitat it can be very hard to spot among grit and stone.
The tubercles are soft and rounded, tipped by areoles that carry only a few weak, spongy spines — a reduced spination that is one of the plant's most distinctive traits and a recurring theme across the schmiedickeanus complex. Flowers appear from the woolly crown, opening white (sometimes with a pinkish tone) and relatively large for so small a plant. Because the whole Turbinicarpus group is so plastic, individual plants vary noticeably in body shape, spine number and flower tone.
Distribution and habitat
The plant is native to north-central Mexico (eastern San Luis Potosí), where members of the schmiedickeanus complex grow on arid limestone hills, ledges and gravel flats. Plants root in shallow, rocky, sharply drained substrates and endure long dry spells, drawing on their swollen taproots and retracting into the ground during drought.
Like all cacti, Turbinicarpus species are listed under CITES, and this genus in particular is given heightened protection because of its small ranges and history of over-collection. Wild plants should never be dug; nursery-raised, seed-grown material is widely available, legal to trade and every bit as satisfying to grow.
Cultivation
Care follows the pattern for the wider Turbinicarpus genus: treat it as a slow, drought-loving miniature that is far more often killed by kindness than by neglect. Grow it in a very free-draining, mostly mineral mix with extra grit, in a pot deep enough to accommodate the taproot, and give it bright light with only light shading from the fiercest afternoon sun.
Water thoroughly but infrequently in the warmer months, always letting the mix dry out completely before the next drink, and keep the plant essentially dry through a cool winter rest. This dry, cold dormancy firms the body, encourages flowering and, above all, guards against rot — the single greatest risk with soft-bodied Turbinicarpus. See Watering and Repotting for general technique.
Propagation
Seed is the standard and most reliable method. The fine seeds germinate readily on a warm, gritty surface kept humid until the seedlings establish, after which they are grown on hard and dry like the adults. Because the plant is typically solitary and offsets sparingly, vegetative propagation is uncommon; where a choice clone is to be bulked up or a weak-rooted plant rescued, growers sometimes turn to grafting. See Propagation — seed for a full walkthrough.
Common problems
- Rot — by far the commonest cause of loss, almost always from overwatering, a slow-draining mix, or water sitting on the crown; the soft body quickly turns brown and mushy.
- Loss of the taproot — cold, wet compost through winter can rot the swollen root even when the top looks sound; keep it dry and cool.
- Etiolation — too little light makes the small body elongate and pale, spoiling its compact form.
- Pests — mealybugs (including root mealybugs on the taproot) and red spider mites are the usual offenders; inspect the crown and roots regularly.
See also
- Turbinicarpus — the genus overview
- Turbinicarpus schmiedickeanus — the complex this plant is usually placed within
- Grafting · Soil and potting mix · Watering · Propagation — seed · Repotting · Pests and diseases