Pelecyphora strobiliformis
| Light | Bright light with a little shade from the harshest afternoon sun |
|---|---|
| Water | Very sparingly; allow to dry completely between waterings, kept bone-dry in winter |
| Soil | Gritty, mostly mineral mix over a deep pot for the taproot (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 10a–11 |
| Propagation | Seed (primary); often grafted to speed slow seedlings |
| Toxicity | Not known to be toxic to cats or dogs |
Pelecyphora strobiliformis is a small, slow-growing cactus from the limestone hills of northeastern Mexico, instantly recognisable by its overlapping, keeled tubercles that spiral around the body like the scales of a spruce or pine cone. This distinctive habit gives it the common name pinecone cactus, and the species was for many years treated as the sole member of its own genus, Encephalocarpus. In spring the flat crown opens with silky magenta to violet-pink flowers.
Description
Pelecyphora strobiliformis is a small, solitary (occasionally clustering) cactus that stays low and rounded, seldom more than a few centimetres across, sitting atop a stout, carrot-like taproot. Its most striking feature is the arrangement of the tubercles: they are triangular and sharply keeled, flattened against the body and overlapping one another in neat spirals, so that the whole plant reads as a green, grey-green or bronzed cone rather than a typical ribbed or warty cactus.
Each tubercle carries a tiny woolly areole near its tip. Seedlings and young plants often bear small, comblike (pectinate) spines, but these are weak and are largely shed as the plant matures, leaving it looking almost spineless. The funnel-shaped flowers emerge from the woolly apex in spring, glossy magenta to purple-pink and quite large relative to the modest body, followed by small dry fruits.
Distribution and habitat
The species is native to the Chihuahuan Desert region of northeastern Mexico, chiefly the states of Nuevo León and Tamaulipas. It grows on limestone hills and rocky flats among desert scrub, usually wedged among stones and often pulled down almost flush with the soil surface in dry weather, where its cone-like body blends easily into the surrounding gravel.
Like many slow, highly sought-after Mexican cacti, P. strobiliformis has been pressured by illegal collection and habitat disturbance. The genus Pelecyphora is listed on CITES Appendix I, the strictest tier, which prohibits commercial international trade in wild-collected plants; artificially propagated specimens can still be traded legally with the correct documentation. Nursery-grown, seed-raised plants are the responsible — and readily available — way to own this species. Collecting from the wild is neither necessary nor permitted.
Cultivation
This is a connoisseur's plant: undemanding in its needs but slow and unforgiving of excess moisture. Grow it in a very free-draining, mostly mineral mix in a pot deep enough to accommodate the taproot, and give it bright light with only light shade from the fiercest summer sun. Water thoroughly but infrequently during the warm growing season, always letting the mix dry out completely first, and keep the plant completely dry and cool through winter — this winter rest both prevents rot and encourages spring flowering.
Because seedlings are so slow on their own roots, many growers graft young plants onto a vigorous rootstock to build size quickly, sometimes returning them to their own roots later for a more natural look. The fleshy taproot dislikes sitting wet, so take particular care at repotting time to let any root disturbance callus before watering again. See Watering for general technique.
Propagation
Seed is the standard and most reliable method. The fine seed germinates on a warm, damp mineral surface and is best raised under humid, bright conditions, though growth is slow and patience is essential. The species rarely produces offsets, so vegetative propagation is uncommon apart from grafting the growing tip or seedlings. See Propagation — seed and Grafting for full walkthroughs.
Common problems
- Rot — by far the commonest killer, almost always from overwatering, a slow-draining mix, or moisture sitting around the taproot; the body softens and discolours from the base.
- Etiolation — too little light spoils the tight cone shape, causing pale, elongated, loosely stacked tubercles.
- Pests — root mealybugs (check the taproot at repotting), mealybugs in the woolly crown, and red spider mites are the usual culprits.
See also
- Pelecyphora — the genus overview
- Grafting · Soil and potting mix · Watering · Repotting · Propagation — seed
- Pests and diseases