Arthrocereus rondonianus aka Snake Cactus

Arthrocereus rondonianus is a small cactus. It belongs to the Cactaceae family. It comes from Brazil, where it grows in rocky ground. Kew places its native range in Serra do Cabral, Minas Gerais. LLIFLE gives a wider range that includes southern Bahia. Its home has a tropical climate with a dry season. Plants grow about 2,950–3,610 feet [900–1,100 metres] above sea level. They grow in groups, at times beneath trees or dry fallen litter. Loss of its wild home threatens this cactus.

This succulent subshrub stores water and branches from the base. It has slim stems that stand upright, lean, or trail across the ground. Stem length ranges from 0.8–2.3 feet [0.25–0.70 metres]. This does not measure the plant's upright height. The bright green stems reach about 0.08 feet [0.025 metres] across. Each has 14–18 low, rounded ribs. Dense groups hold 40–50 fine radial spines, which spread outwards. These may look greenish yellow, gold, or reddish brown. Each group has one or two longer spines at its centre.

The pink to purple-pink flowers open at night and give off scent. Their pink blooms differ from those of many night-flowering cacti. Flowers grow on the sides near the ends of stem joints. Each can reach about 0.26 feet [0.08 metres] long. The long, thin flower tubes bear wool and fine, hairlike spines. LLIFLE links their scent to the spread of pollen by moths. The round, green fruits have scales on their skin.

This cactus grows fast in gardens but needs some care. LLIFLE reports that grafted plants grow better. Stem cuttings take root with ease, though. A greenhouse helps it grow, and it prefers mild winters. Give it a cactus mix with many pores and good pot drainage. It needs acidic compost. Mixes rich in lime can stop growth. Filtered sun or shade in the afternoon suits it. Indoors, it needs bright light with some direct sun. Strong light can turn stems bronze and spur flowers and spines.

Give more water in summer than many other cacti need. Yet cool, wet sites can cause rot. The risk is greater when it grows on its own roots. Long spells with no moisture also cause problems. LLIFLE suggests a summer feed rich in potassium. Its scented night flowers give it value as a plant to collect. Still, few people keep it in collections.