Cleistocactus colademononis aka Monkey Tail

The Cleistocactus colademononis, commonly known as the monkey tail cactus, is an attractive cactus with light green, cylindrical stems densely covered with white, hair-like spines. It branches at the base and grows as an epilithic cactus on rocks in its natural habitat. The stems can grow up to 6 feet long and 2.5 inches in diameter. It grows upright at first, becoming pendulous with age.  The bright red flowers appear from late spring to early fall. They can reach a length of 3" and a diameter of 2".