Weberbauerocereus rauhii
| Light | Full sun to very bright light; loves all the direct sun it can get |
|---|---|
| Water | Moderate in the growing season, allowing the mix to dry between soakings; keep dry and cool in winter |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Best kept above freezing; tolerates brief light frost when bone dry (roughly USDA zones 9b–11) |
| Propagation | Seed; also from stem cuttings |
| Toxicity | Not known to be toxic to cats or dogs, though the spines are hazardous |
Weberbauerocereus rauhii is a tall, columnar cactus native to the arid valleys of southern Peru, prized in cultivation for its strong, golden spines and its bold, tree-like silhouette. In habitat it forms branching, upright stems several metres high, and in gardens it makes a striking architectural centrepiece for a dry, sunny landscape. It belongs to the South American genus Weberbauerocereus.
Description
Weberbauerocereus rauhii is a large columnar cactus that grows shrubby to tree-like, developing a short trunk and branching into a candelabra of erect green stems up to about 6 metres tall. Individual columns are strongly ribbed, with closely set areoles running the length of each rib. Each areole bears several very strong yellow central spines, darker at the tip and up to 6–7 cm long, together with numerous much shorter whitish-grey radial spines. The stout central spines take on a warm golden tone in strong light, standing out against the green body beneath.
Mature plants produce tubular, somewhat asymmetrical flowers that open toward night and into the early morning, in muted shades of white, cream and dull pink. As with many night-blooming columnar cacti, the blooms are adapted for pollination by nocturnal visitors, chiefly bats. Flowering generally comes only on well-established, sizeable specimens.
Distribution and habitat
The species is endemic to Peru, where it grows on dry, rocky slopes and in arid inter-Andean valleys of the south at roughly 500–2500 metres, in a region of very low rainfall. Plants there endure intense sunlight, sharp drainage and long dry spells, relying on occasional seasonal rains. This background explains its love of sun and its dislike of soggy roots in cultivation.
Cultivation
Weberbauerocereus rauhii is a rewarding, undemanding grower for anyone who can give it enough light and warmth. Plant it in a very free-draining, mostly mineral mix and site it in full sun, where the strong light keeps growth compact and encourages the best golden spination. Etiolation (thin, pale, stretched growth) is the usual sign of too little light.
Water moderately through the warm growing months, letting the mix dry out well between soakings, and then keep the plant dry and cool over winter to prevent rot and to help ripen the stems for flowering. It appreciates room for its roots and benefits from occasional feeding in summer; see Watering and Repotting for general technique. In frost-prone climates it is best grown in a container that can be moved under cover, or in a greenhouse, though established plants kept dry will shrug off a little brief cold.
Propagation
The species is readily raised from seed, sown on a warm, gritty surface and kept humid until the seedlings establish; see Propagation — seed. It can also be grown from stem cuttings — a section of column is removed with a clean blade, the cut face allowed to callus for a week or more in a dry, shaded spot, and then set on barely moist mix until roots form. See Propagation — cuttings for the full method.
Common problems
- Rot — the most common cause of loss, almost always from overwatering or a slow-draining mix, especially in cold weather; stems soften and discolour from the base.
- Etiolation — grown in too little light, the stems become pale, thin and drawn out, with weaker spination.
- Pests — mealybugs (white fluff among the areoles) and red spider mites (fine webbing and bronzed skin) are the usual offenders; see Pests and diseases.
See also
- Weberbauerocereus — the genus overview
- Soil and potting mix · Watering · Repotting
- Propagation — seed · Propagation — cuttings