Isolatocereus dumortieri

Isolatocereus dumortieri, the candelabra cactus, is native only to Mexico. It belongs to the cactus family, Cactaceae. Sources also list it under the name Stenocereus dumortieri. It grows across central and southern Mexico in dry scrub. It also occurs in grasslands and forests that shed their leaves. Wild plants grow on rocky slopes, hillsides and cliffs. The species has a wide range and can be locally abundant. Useful Tropical Plants reports its 2017 IUCN status as Least Concern.

This tree-like cactus has a woody trunk and many upright branches. The branches bend inward slightly and narrow at intervals. Their pale blue-green skin can have a waxy look. Each stem has about five to eight triangular ribs. Small, felted areoles sit close together along the ribs. They bear pale yellow or straw-coloured spines that darken with age. Wild plants reach about 49 feet [15 metres] tall. Plants grown in gardens or glasshouses often stay smaller. RHS lists height above 39 feet [12 metres], without a fixed upper limit. Its spread range is 13–26 feet [4–8 metres]. Plants can take 20–50 years to reach full size.

Mature plants bear small flowers near the stem tips. The pale green or white blooms open at night. They can stay open until midday and have no scent. RHS gives summer as the flowering season in cultivation. In Mexico, reproduction runs from January until July's final fruit fall. The oval fruits turn red and have red-orange flesh. They lack spines and split open when ripe. Birds, bats and insects feed on flowers and fruits. Ringtails eat the fruit and seeds, while bats spread seeds.

Grow this cactus in full sun with shelter from cold. Use a cactus mix that lets water drain fast. RHS lists sandy and loamy soils across the pH range. Give moderate water during growth, then keep it dry in winter. Its H2 rating means it cannot survive freezing. In Britain, grow it under glass or in patio pots. Move patio plants into a greenhouse for winter. Its tall, branched shape suits planting where form matters. RHS also lists it for houseplant and conservatory use.

No routine pruning is needed, and RHS reports few disease problems. Mealybugs and scale insects may attack the stems. Aphids may appear when the plant flowers. Propagate it from spring-sown seed or summer stem cuttings. People eat the fruit and harvest wood for fences. Other uses include hunting torches and fuel for temazcales. Useful Tropical Plants records no known medicinal uses or hazards. That does not establish safety for every part or for pets.