Melocactus bahiensis
| Light | Bright light to full sun once established; some acclimatisation needed |
|---|---|
| Water | Regularly in warm growth, allowed to dry between waterings; keep dry and warm in winter |
| Soil | 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 bahiensis is a small, globular to slightly barrel-shaped melon cactus from the dry interior of eastern Brazil, best known for its stout spines and, in mature plants, the woolly, bristly cephalium that crowns the top. It is a variable species — body size, rib count, and spine colour differ noticeably from one population to the next — and is widely grown from seed by collectors who prize its neat form and the red-bristled cephalium it develops with age.
Description
Melocactus bahiensis forms a solitary, firm green body that is depressed-globose to short-barrel shaped, typically reaching around 10–20 cm in diameter. The body carries a moderate number of prominent ribs (roughly 8–14) edged with stout areoles. The spines are stout and rigid, mostly straight but sometimes curved or hooked — hooked spines are especially common on young plants — and range from pale amber and yellowish through reddish-brown to nearly grey, often with a greyish cast; the central spines are usually the heaviest. Spine colour and curvature vary considerably across the species' range, which is part of what makes it a favourite among growers who enjoy comparing forms.
Like all melon cacti, a mature plant stops growing taller at the vegetative body and instead produces a cephalium — a dense, felted cap of wool and fine bristles from which the flowers and fruit emerge. In this species the cephalium is comparatively small and typically white-woolly shot through with reddish bristles. Small pink to magenta flowers push out of the cephalium and are followed by slender, club-shaped pink to reddish fruit.
Distribution and habitat
The species is native to eastern Brazil, centred on the state of Bahia (from which it takes its name) and extending into neighbouring Pernambuco and Minas Gerais. It grows on exposed rock — crystalline outcrops (quartzitic-arenitic, granite/gneiss), quartz gravel, and stony slopes — in the scrubby caatinga and in campo rupestre (rocky montane grassland), at elevations of roughly 300–1,300 m, often rooted in shallow pockets of mineral soil in full exposure. Rainfall is strongly seasonal, and plants endure a long dry period each year.
As with the whole cactus family, Melocactus is listed under CITES Appendix II, so wild collection and cross-border trade of habitat plants are regulated; nursery-grown, seed-raised plants are common and legal to own and trade.
Cultivation
Melocactus bahiensis is a warmth-loving cactus and less forgiving of cold and damp than many globular species — this is the main thing to get right. Grow it in a very free-draining, mostly mineral mix in a pot that drains freely, in bright light building up to full sun once the plant is acclimatised. Water generously through the warm growing season, letting the mix dry out between waterings, then keep the plant dry and warm over winter. Cold, wet roots are the quickest route to rot.
Give the plant as much winter warmth as you can manage; unlike hardier desert cacti it resents a cold, damp rest and prefers a minimum well above freezing. See Watering and Repotting for general technique. Note that once a plant has begun its cephalium it will not grow any larger in the body, so patience through the vegetative years is part of growing this genus.
Propagation
Seed is effectively the only method, as the species stays solitary and does not offset. The seeds are small and germinate on a warm, moist mineral surface; steady warmth is the key to good germination and early growth. Growth is slow to moderate, and it takes several years for a seedling to reach flowering size and form its cephalium. See Propagation — seed for a full walkthrough. Grafting is sometimes used to speed up choice seedlings, though most growers raise this species on its own roots.
Common problems
- Rot — the commonest cause of loss, almost always from cold combined with excess moisture or a slow-draining mix; the body softens and discolours from the base.
- Cold damage — this species is more cold-sensitive than typical desert cacti and may mark or collapse if kept cold and wet in winter.
- Etiolation — too little light makes the body pale and elongate and weakens the characteristic heavy spination.
- Pests — mealybugs (white fluff in the areoles and roots) 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 · Repotting · Propagation — seed · Pests and diseases