Disocactus ackermannii aka Orchid Cactus

Disocactus ackermannii, the red orchid cactus, comes from southern Mexico. It belongs to the cactus family, Cactaceae. This evergreen perennial grows on trees as an epiphyte. Its roots grip bark beneath the forest canopy. Some plants also grow on rocks. Its flat stems and large red blooms suit hanging baskets. Growers also use it in pots, greenhouses and frost-free gardens.

Plants form clumps with branches that rise, then hang down. Garden height is about 1–1.6 feet [0.3–0.5 m]. The RHS gives a spread up to 1.6 feet [0.5 m]. LLIFLE reports wider clumps, reaching 2–3.3 feet [0.6–1 m]. Individual stems can reach 3.3 feet [1 m]. The fleshy stems look like leaves and have scalloped edges. Clear veins run through their flat sections. Their bases are round rather than flat. Young growth starts brownish and turns dark green. Short bristles occur on young and lower growth, without large spines.

Spring brings large, curved flowers shaped like funnels. Their red shades range from crimson to scarlet. Blooms span about 0.36–0.46 feet [0.11–0.14 m]. They open during the afternoon or evening. Each can stay open through day and night for three days. The oval to oblong fruits turn green to brownish red. They reach about 0.13 feet [0.04 m] long. People eat the pale pinkish-white pulp raw. Useful Tropical Plants reports no known hazards. This does not establish safety for pets or every plant part.

Give this forest cactus bright, filtered light or partial shade. Use acidic compost that holds moisture but drains well. An epiphytic cactus mix suits its roots. Water well during growth, allowing slight drying between waterings. Keep the mix moist during bloom, but never soggy. Reduce watering in winter and stop feeding. During growth, apply half-strength feed for acid-loving plants every two weeks. The RHS rates it H1C, so protect it from frost. In Britain, outdoor growing is limited to the warmer months.

Avoid moving plants once flower buds have formed. A change in their surroundings can make buds fall. Poor drainage can cause root rot. Scale insects and mealybugs may attack plants under glass. The RHS reports few other disease problems and requires no routine pruning. Take softwood cuttings in late spring, or raise plants from seed. Plants may take five to ten years to reach full size. Useful Tropical Plants records a 2017 Least Concern assessment. Some wild populations face habitat loss, though the species remains widespread.