Aporocactus flagelliformis aka Rat Tail Cactus

Aporocactus flagelliformis is the rat's tail cactus. Another name is whip cactus. Sources also call it Disocactus flagelliformis. It belongs to the cactus family. This succulent stays green all year. It comes from Mexico. Records place it in several eastern states. Sources differ on where it grows. Some cite dry forest; others cite cloud forest. It grows on trees as an epiphyte, or on rocks. Useful Tropical Plants lists its status as Near Threatened in 2017. Farms and grazing cause forest loss, which threatens wild plants.

Stems grow in a cluster from the plant's base. Young stems stand up at first. Then they trail, hang, or sometimes climb. Garden plants reach about 0.3 feet [0.1 metres] high. Their spread reaches 3.3–4.9 feet [1–1.5 metres]. Long stems can reach 6.6 feet [2 metres] or more. They start green, then turn grey-green with age. Each round stem has seven to twelve low ribs. Small white areoles, which bear spines, line the ribs. These spots sit close together. The fine spines look like bristles. Their shades range from red-brown to red-yellow.

Flowers grow from the sides of the stems in spring. LLIFLE places the main bloom in mid to late spring. The flowers open by day and have no scent. Each lasts three to five days. Each flower forms a funnel that bends upward. Its two sides match. Shades range from red to deep pink and purple-pink. Pale pink or white stamens stick out from the flower. The small, round fruits bear red bristles. Their flesh has a yellow tint. Their oval seeds are brownish red.

Grow it in a cactus mix that drains well. RHS calls for bright light through a filter. LLIFLE allows stronger sun. Give modest amounts of water while it grows. Give less water in the cooler months. LLIFLE says to water well, then let the mix dry. RHS calls for high-potash feed each month while it grows. Its H1C rating suits outdoor use in summer. It does not suit year-round exposure. Sources differ on how well it bears frost. It thus needs shelter in winter. LLIFLE reports brief survival at −4°C. Useful Tropical Plants says it cannot bear frost.

Its trailing stems suit hanging baskets and pots. They also suit sheltered patios in summer. LLIFLE calls this cactus easy to grow and fast-growing. RHS gives five to ten years to reach full size. Growers can raise it from seeds or stem cuttings. It needs no routine pruning. Growers may still cut off old brown stems. Scale insects and mealybugs may attack it. RHS reports few disease problems. Sources record no edible uses. Mexican folk medicine uses dried flowers for heart complaints. Reports also describe internal use of its caustic juice. This use is dangerous.