Rebutia arenacea
| Light | Bright light with some protection from harsh midday summer sun; happy in a cool, airy spot |
|---|---|
| Water | Regularly through the growing season, letting the mix dry between waterings; keep dry and cool in winter |
| Soil | Gritty, free-draining mineral mix (see Soil and potting mix) |
| Temperature | Cool-growing; tolerates cold if kept bone dry. Roughly USDA zones 9a–11, with a dry winter rest near freezing |
| Propagation | Seed and offsets |
| Toxicity | Non-toxic to cats and dogs |
Rebutia arenacea is a small, flattened, globular cactus from the Bolivian highlands, prized by collectors for its neat, comb-like (pectinate) spines pressed close against the body and its generous flush of golden-yellow to orange flowers. It is sometimes placed in the segregate genus Sulcorebutia (as Sulcorebutia arenacea) and, in treatments that merge Sulcorebutia into Weingartia, as Weingartia arenacea; most hobbyists now file it within a broadly defined Rebutia.
Description
Rebutia arenacea forms a low, somewhat flattened globe, usually solitary or slowly clustering with age, seated tightly against the soil. The body is a dull green to bronzed green, divided into small tubercles arranged in gentle spirals. Each areole carries a tidy row of short, comb-like spines that lie flat and curve back toward the body, giving the plant its characteristic combed, symmetrical look and a soft-to-the-touch appearance despite the spination.
Flowers appear in spring from areoles low on the sides of the plant, a habit typical of Sulcorebutia-type species. They are golden-yellow to orange and open wide in sunshine over several days, often nearly smothering a well-grown plant. The fleshy taproot below is substantial and prone to rot if kept wet.
Distribution and habitat
The species is native to Bolivia, where it grows in the high inter-Andean valleys among rocks and coarse, gritty soils. Plants of this group generally occupy exposed, seasonally dry mountain sites that are bright and airy, cold at night, and subject to a marked dry season. In habitat they often sit wedged among stones with the taproot anchored in mineral debris rather than rich earth.
Cultivation
Rebutia arenacea is an excellent beginner's cactus: small, free-flowering and forgiving, provided its roots are never left sitting in wet soil. Grow it in a very gritty, mostly mineral mix in a pot deep enough to accommodate the taproot, in bright light with a little shade from the most intense summer sun. Water freely while it is in active growth, always allowing the mix to dry between waterings.
Like most highland Rebutia, it is cool-growing and needs a cold, completely dry winter rest to flower well the following spring; kept dry, it tolerates surprisingly low temperatures. Overwatering and a soggy mix are the main causes of loss. See Watering and Repotting for general technique.
Propagation
The species grows readily from seed, which germinates easily on a warm, gritty surface kept humid until the seedlings establish; see Propagation — seed. Older plants that offset can be increased by removing rooted or unrooted pups and treating them as offsets — let any cut surface callus before potting into a dry, gritty mix. Choice clones are sometimes maintained vegetatively to keep flower colour consistent.
Common problems
- Rot — the fleshy taproot and body rot quickly in a wet or slow-draining mix, especially over winter; keep dry and cold at rest.
- No flowers — usually the result of too warm or too wet a winter; the plant needs a genuine cold, dry dormancy to bloom.
- Pests — mealybugs (including root mealybugs on the taproot) and red spider mites are the usual offenders; see Pests and diseases.
See also
- Rebutia — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — offsets
- Pests and diseases