Espostoa senilis
| Light | Bright light to full sun; a little shade eases the hottest afternoons |
|---|---|
| Water | Moderate in the warm months, always drying out between soakings; keep dry and cool in winter |
| Soil | Very free-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; happiest in USDA zones 9b–11 |
| Propagation | Seed, and stem cuttings from mature plants |
| Toxicity | Non-toxic to cats and dogs |
Espostoa senilis is a slender, white-haired columnar cactus from the dry inter-Andean valleys of Peru, once placed in the genus Thrixanthocereus and still sold under that name. It is prized among collectors for the dense, silky wool that veils the whole stem, giving mature plants the soft, hoary look that inspired the epithet senilis ("old", "aged"). Care follows the rest of its genus; see Espostoa for the wider group.
Description
Espostoa senilis grows as an erect, mostly solitary column that branches sparingly, if at all, and reaches well over a metre in age. The stem is comparatively narrow and finely ribbed, and every rib carries closely set areoles that produce both fine radial spines and a long, hair-like wool. This wool is the plant's signature: it is soft, silky and abundant enough to wrap the green body in a pale, silvery fleece, through which slender yellowish central spines project.
Like others in the genus, a flowering-age plant develops a cephalium — a specialised zone of dense wool and bristles along one side of the stem — from which the flowers emerge. The blooms are nocturnal and tubular, an unusually deep pink for the genus, opening at night and typically pollinated by moths or bats; they are followed by small fleshy fruits.
Distribution and habitat
The species is native to Peru, where it grows on rocky slopes and in the seasonally dry scrub of the warm inter-Andean valleys. In habitat it endures strong sun, sharp drainage and a pronounced dry season, and the heavy coat of wool helps shade the stem from intense light and buffer it against swings in temperature.
Cultivation
Espostoa senilis is a rewarding column for a bright windowsill or greenhouse, though it is a little more demanding than the toughest desert cacti. Grow it in a very free-draining, mostly mineral mix and give it the brightest position you can, as strong light keeps the growth compact and the wool dense. Water generously while it is actively growing in the warm months, always letting the mix dry out before watering again, and keep it dry and cool through winter to prevent rot and preserve the appearance of the wool. Avoid letting it sit cold and wet, which is the quickest route to basal rot. See Watering and Repotting for general technique.
A practical note on the wool: overhead watering and dust will gradually mat and discolour the hair, so water at the base where you can and keep the plant somewhere clean and airy.
Propagation
Fresh seed is the usual route and germinates well on a warm, gritty surface kept humid until the seedlings establish; see Propagation — seed. Mature plants can also be grown from stem cuttings, which should be left to callus for a week or more before being set on barely moist mineral mix to root. Because the species rarely offsets, cutting propagation generally means taking a section of an established column rather than harvesting pups.
Common problems
- Rot — almost always from overwatering, a slow-draining mix, or cold wet winters; the stem softens and discolours, usually from the base.
- Matted, dirty wool — overhead watering, dust and mineral spotting dull the silvery coat; keep water off the stem and the plant in a clean spot.
- Etiolation — too little light thins the wool and stretches the growth, spoiling the plant's character.
- Pests — mealybugs love to hide in the dense wool where they are easy to miss, and red spider mites can bronze the stem; inspect regularly. See Pests and diseases.
See also
- Espostoa — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings · Repotting