Hedge Cactus is a columnar cactus branching from the base, up to 30 feet tall, native to South America. The plant is much smaller, if grown in a pot. Stems are 4-8 inches in diameter, with 5 to 8 ribs. This cactus blooms at night. Its large flowers, 6 inches or more across, last into the early morning hours. Once the sun rises, the flower closes up and dies.