Disocactus speciosus aka Sun Cereus

Disocactus speciosus is an evergreen cactus known as sun cactus. It belongs to the cactus family, Cactaceae. Its native range runs from Mexico to Guatemala. Kew places it in a tropical climate with seasonal drought. It grows on other plants or on rocks. LLIFLE lists Heliocereus speciosus as a synonym of this species. Its Spanish names include Santa Marta and Pitaya de Cerro.

This cactus forms clumps with a low, mounded shape. The RHS gives a cultivated height of 0.3–1.6 feet [0.1–0.5 metres]. It gives the same range for the plant's spread. Plants take five to ten years to reach mature size. The slim stems have angles and grow upright or slope upward. They bear spines that range from yellow to pale brown. The RHS classes the plant as evergreen.

The flowers have a trumpet shape and reach 0.56 feet [0.17 metres] across. The RHS describes red blooms with purple tones on the sepals. Chicago Botanic Garden lists the flower colour as pink. Its flowering record spans May through August. These sources differ on colour, but both describe this same species. The supplied accounts give no details about its fruit. They also provide no evidence for edible parts or human and pet safety.

For pot culture, the RHS calls for an epiphytic cactus mix. It recommends bright light filtered from direct sun and high humidity. Both garden profiles also list full sun as an exposure. The RHS lists loam or sand, with acid or neutral pH. The growing mix must drain well. Water moderately while the plant grows, then keep it barely moist through winter. Feed monthly during growth with a balanced liquid feed at half strength. The RHS rates it H1B, allowing summer outdoor growth in Britain. That rating gives a temperature range of 10–15°C. Chicago Botanic Garden lists USDA zones 10–12.

The RHS suggests this cactus for containers and patio displays. It also lists it among plants that need little upkeep. A sheltered site suits its stated growing needs. It needs no routine pruning, and the RHS reports few disease problems. Mealybugs can still attack, so check plants for these pests. Growers can raise new plants from seed or offsets. Sow seed in early spring at 19–21°C.