Disocactus flagelliformis, or rat-tail cactus, is a species of cacti in the Cactaceae family. It is native to Mexico, but is cultivated throughout Central and South America. The rat-tail cactus's most recognizable characteristic is its long spiny stems that hang from it like dreadlocks. This easy-to-grow species of cacti can be planted directly in the ground in hot climates and in container gardens in cooler climates. It is susceptible to some common plant diseases and common plant pests.
The rat-tail cactus, also called red tail cactus, thrives in hot, dry climates, such as U.S. Department of Agriculture Hardiness Zones 9-11. This means that 30° Fahrenheit (-1.1° Celsius) is its coldest tolerable temperature. It needs full sun or partial shade and does best if the lighting comes from the south or west in the northern hemisphere. General-purpose cactus mix with a pH level that is mildly acidic, neutral, or mildly alkaline should be used instead of regular potting mix or compost.
Generally, these cacti grow to be between 18 to 24 inches (45-60 cm) tall and are about 18 inches (45.7 cm) wide. They have long, thick, spiny stems that can grow to be up to 6 feet (1.8 m) long. A young rat-tail cactus has green stems that turn gray as it ages. In late spring on through early summer, the plant produces small, bright pink flowers 1-1/2 inches (4 cm) long and 2-1/2 inches (6 cm) wide. The flowers open during the day and close at night.
In its natural habitat, hummingbirds pollinate the cacti's flowers; cultivated plants usually need to be pollinated by hand, however. The rat-tail cactus is usually propagated through stem cuttings. After cutting the stem, it should be allowed to dry until the cut begins to heal. At that time, it can be replanted and a new cactus will grow, blooming in the following two or three years. Summer is the best time to take a cutting. Gardeners should consider wearing heavy work gloves whenever handling cacti.
In the wild, the rat-tail cactus is epiphytic. This means that it takes root in the crevices of trees and uses rotting leaves as food. The cactus is not parasitic, as the host tree is neither harmed nor used as food. Growing naturally in a tree makes the rat-tail cactus particularly suited for hanging baskets. Rat-tail cacti can also be grown in rock gardens, in containers, or kept as houseplants.
These cacti are susceptible to root rot if is given too much water or if planted in poorly draining soil. Red spider mites, mealy bugs, and scale may also attack the cactus. Infestations may be overlooked if the plant is kept in a hanging basket, so periodic checks should be made. The spines make it difficult to pick the insects off by hand, so the usual course of action is to use a systemic insecticide made especially for cacti. Aside from this issue, this plant requires little attention and makes a unique addition to the home.