Acanthocereus tetragonus aka Fairies Castle

Acanthocereus tetragonus is a cactus with spines. Its long stems arch. It belongs to the cactus family, Cactaceae. People call it barbed wire cactus and night-blooming cereus. Its native range starts in southern Texas and reaches Venezuela. It also grows in southern Florida and the Caribbean. Kew places it in tropical areas with a dry season. Useful Tropical Plants describes its home as dry tropical land. It also includes subtropical land.

This succulent has no leaves. It grows as a shrub and can scramble or climb. Sources give heights of about 6.6–23 feet [2–7 metres]. Useful Tropical Plants gives another height: 13 feet [4 metres]. These figures do not set a clear garden size range. The stems can reach about 0.16 feet [0.05 metres] across. They arch rather than grow only as upright columns. Some stems take root where they touch the ground. These roots let stems on the ground form new growth points. The plant keeps its green growth all year.

White flowers open at night. Hawkmoths pollinate them, moving pollen between flowers. The supplied species evidence gives no bloom season. The bright red fruit tastes sweet and has juicy flesh. Some fruits have an egg shape; others are longer and oval. Each fruit measures about 0.10–0.26 feet [0.03–0.08 metres] long. Local people pick fruit and stems from wild plants. They eat the fruit raw and cook the tender young stems. Sellers sell the fruit at local markets in Guatemala.

In the wild, this cactus grows in sandy coastal soils. It grows in dense thickets and hammocks. It also grows on low-lying coastal land. Known sites range from sea level to 33 feet [10 metres]. In gardens, it needs sun and soil that drains well. Useful Tropical Plants calls for sandy soil with little humus. It gives a preferred soil pH of 6–7.5. The supplied species sources give no firm frost limit. Nor do they give a hardiness zone.

People grow this cactus as a living fence and boundary marker. Its spiny growth forms a barrier along the planted line. Useful Tropical Plants reports use as medicine but gives no details. It lists no known hazards. This does not prove that the plant is safe for pets. It reports no specific pests or diseases for the species. It cites a 2017 IUCN assessment of Least Concern. The plant remains widespread and abundant. That account reports no known threats.