Melocactus peruvianus
| Light | Bright light to full sun; acclimatise gradually to avoid scorch |
|---|---|
| Water | Moderate in warm growth, sparingly in winter; never leave standing wet |
| Soil | Gritty, fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Warmth-loving; keep above about 10 °C, USDA zones 10–11 |
| Propagation | Seed |
| Toxicity | Non-toxic to cats and dogs |
Melocactus peruvianus is a globular to short-barrel melon cactus from the coastal deserts and dry valleys of Peru. Like all melon cacti it is celebrated for the cephalium — a distinct woolly, bristly cap of felt and spines that crowns a mature plant and from which its small flowers and fruit emerge. The species is notably variable in body colour and in the length and curve of its ribs' spination, a variability that has made it a favourite among collectors and an easy, rewarding plant to raise from seed.
Description
Melocactus peruvianus forms a solitary, ribbed green to grey-green body, typically globular when young and becoming more barrel-shaped with age. The ribs are prominent and carry areoles set with stiff spines that range from nearly straight to strongly curved, varying considerably from plant to plant — one of the traits that makes the species so popular with growers who enjoy selecting distinctive forms.
At maturity the plant stops enlarging its green body and produces a cephalium at the apex: a dense cap of white wool studded with fine reddish bristles. All flowering happens from this structure. The small pink flowers push up through the wool and are followed by slender, reddish, berry-like fruit. Once the cephalium has begun to form, the plant is effectively adult and will not resume ordinary body growth.
Distribution and habitat
The species is native to Peru, where it grows in the arid coastal lowlands and inland dry valleys of the western slopes. Plants root in rocky, gritty ground in a hot, low-rainfall climate moderated in places by coastal fog. As with much of the genus, Melocactus peruvianus encompasses a range of local forms across its distribution, and the boundaries between it and neighbouring Peruvian melon cacti are treated differently by different authors.
Like the entire cactus family, Melocactus is listed under CITES Appendix II, so international trade is regulated; nursery-raised, seed-grown plants are widely and legally available.
Cultivation
Melocactus peruvianus is a warmth-loving cactus and one of the more approachable melon cacti in cultivation, though it dislikes cold and prolonged damp. Grow it in a very free-draining, mostly mineral mix in bright light to full sun, giving young plants a little acclimatisation to avoid scorch. Water moderately through the warm growing season, always letting the soil dry between waterings, and keep the plant much drier and warm through winter. See Watering and Repotting for general technique.
Warmth is the key to good results: unlike many high-altitude cacti, coastal Melocactus resent a cold, wet rest and are prone to root loss and basal rot if kept too cool and moist. Where winters are cold, a heated position and a strictly dry rest pay off. Mature, cephalium-bearing plants are best left undisturbed as far as possible.
Propagation
Seed is the standard and essentially the only practical method. Melocactus peruvianus is solitary and does not offset, so there are no pups to remove and vegetative propagation is not normally an option. The seed germinates readily in warmth on a mineral surface kept humid, and seedlings grow at a reasonable pace with steady heat. See Propagation — seed for a full walkthrough.
Common problems
- Rot — the commonest cause of loss, almost always from a cold, wet winter rest or a slow-draining mix; the body softens and discolours from the base.
- Cold damage — this is a warmth-loving species, and low temperatures (especially combined with damp) cause corky scarring or collapse.
- Etiolation — too little light makes the body pale and drawn, distorting its natural shape.
- Pests — mealybugs (white fluff in the areoles and cephalium) and red spider mites (fine webbing, bronzed skin) are the usual offenders; see Pests and diseases.
See also
- Melocactus — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Repotting · Pests and diseases