Tephrocactus weberi
| Light | Full sun to very bright light |
|---|---|
| Water | Sparingly in the growing season; keep bone dry and cool in winter |
| Soil | Very gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; happiest in warm, airy conditions |
| Propagation | Detaching segments (offsets); seed |
| Toxicity | Not known to be toxic to cats or dogs; spines are the main hazard |
Tephrocactus weberi is a low, clustering cactus from the dry uplands of northwestern Argentina, built from short cylindrical segments that pile up into dense mounds. It belongs to the segmented South American genus Tephrocactus, and is known for its variable spination — the areoles bear needle-like, more or less flexible, interlacing spines that range in colour from yellow to reddish and vary considerably in length and density from plant to plant.
Description
Tephrocactus weberi grows as a chain of small, cylindrical segments (joints), each typically 3–10 cm long and about 2 cm thick, that break apart easily and re-root to form spreading clumps. The joints are firm and grey-green, often flushed darker in strong sun and cold, and carry closely set, well-defined tubercles.
The most variable feature is the spination. Each areole bears roughly five to ten spines (fewer in some forms), needle-like and more or less flexible, interlacing, and up to about 5 cm long; the lower spines are usually thinner and pressed against the stem. Spine colour ranges from yellow to reddish, and can be bright, while some forms carry creamy-white bristly spines. Because plants differ so much, growers often select and name forms for their spine density and colour.
Flowers, when they appear on mature plants, are borne at the tips of segments and are yellow — typically lemon to golden yellow — up to about 3 cm long, though orange- and pink-flowered forms are known. The species is grown far more for its form and spines than for its bloom.
Distribution and habitat
The species is native to northwestern Argentina — recorded from Salta, Catamarca, Tucumán, La Rioja and San Juan provinces — where it grows on rocky mountain slopes and open, stony ground, roughly between 550 and 2000 m elevation. Plants endure a climate of strong sun, wide day-to-night temperature swings, and a long, cold, dry winter — conditions that shape the compact, well-armoured growth seen in habitat.
Cultivation
Like most Tephrocactus, T. weberi is undemanding once its two firm rules are respected: lots of sun and very sharp drainage. Grow it in a mostly mineral mix with plenty of grit or pumice, in the brightest position you can offer — good light is what keeps the joints tight and encourages the best spine development.
Water thoroughly during warm, active growth, always letting the mix dry out completely before the next drink, and stop almost entirely through winter. A cold, bone-dry winter rest is important: kept dry, the plant tolerates a surprising amount of cold, but any excess moisture in cool conditions invites rot. See Watering and Repotting for general technique, and take care handling the plant, as the joints detach at a touch and the spines are sharp.
Propagation
Propagation is easy and mostly happens by accident. Segments that fall or are knocked off will root readily when set on top of a gritty mix and kept barely moist and warm — see Propagation — offsets and Propagation — cuttings. Allow the broken surface to callus for a few days before setting it down to reduce the chance of rot.
Seed is also viable, though germination can be slow and erratic; see Propagation — seed. Because segments detach so freely, vegetative increase is by far the more common method in cultivation.
Common problems
- Rot — from overwatering, a slow mix, or damp cold in winter; segments soften, discolour and drop.
- Etiolation — too little light produces stretched, pale joints and weak spines, and the clump loses its compact shape.
- Pests — mealybugs (white fluff hidden among the areoles and joint bases) and, in dry stagnant air, spider mites.
- Shattering — the joints are famously loose; a knock can scatter segments, so handle and repot with care.
See also
- Tephrocactus — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — offsets · Propagation — cuttings · Propagation — seed
- Pests and diseases