Acanthocereus tetragonus is a species of cactus that is native to southern Florida and the Lower Rio Grande Valley of Texas in the United States, Mexico, Central America, Caribbean, and northern South America. Common names include night-blooming cereus,barbed-wire cactus,sword-pear,dildo cactus,triangle cactus, and rgano-alado de pitaya (Spanish). It was originally described by Carl Linnaeus in 1753 as Cactus tetragonus but was moved to the genus Acanthocereus in 1938 by Pieter Wagenaar Hummelinck.
Acanthocereus tetragonus is a tall, columnar cactus that reaches a height of 2-7 m (6.6-23.0 ft). Stems are dark green, have three to five angles, and are 6-8 cm (2.4-3.1 in) in diameter. Areoles are grey and separated by 2-3 cm (0.79-1.18 in). Central areoles have one to two spines up to 4 cm (1.6 in) long, while radial areoles have six to eight spines up to 2.5 cm (0.98 in) in length. The flowers are 14-20 cm (5.5-7.9 in) in diameter with a tube 8-15 cm (3.1-5.9 in) in length. Outer tepals are greenish-white, inner tepals are pure white, and pistils are creamy white. Flowers are open from midnight until dawn, attracting hummingbird moths (Hemaris spp.). The shiny, red fruits are around 5 cm (2.0 in) long.
Young stems of the barbed-wire cactus can be eaten as a vegetable either cooked or raw, while the fruits are edible and sweet. It is sometimes cultivated as an ornamental. The Fairy Castle Cactus, a miniature cultivar of this species, has many curved branches that resemble the turrets of a castle.