Acanthocereus tetragonus is a species of cactus native to Florida, Texas, Mexico, Central America, Caribbean, and northern South America. Common names include night-blooming cereus, barbed-wire cactus, sword-pear, dildo cactus, triangle cactus.
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. 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. The shiny, red fruits are around 5 cm (2.0 in) long. This highly spiny, often large, and thicket-forming cactus has stems up to 10 feet or possibly taller. It is native to the coastal hammocks and hot, dry coastal habitats and thickets and sandy coastal habitats. The flowers are showy and are white with a deep red and orange or red-orange center. The flowers bloom at night and close during the day. This cactus often forms thickets in coastal hammocks which can be impenetrable and spiny.