Opuntia leucotricha aka Aaron's Beard Prickly Pear

Opuntia leucotricha is a cactus native to Mexico. Kew records it in Querétaro and San Luis Potosí. It grows in desert and dry shrubland. Common names include semaphore cactus and Aaron's beard prickly pear. It belongs to the cactus family, Cactaceae. This succulent forms shrubs, clumps, or small trees. Plants often reach 10–16 feet (3–5 metres) tall. Tree forms have a clear trunk and broad crown.

Long white bristles cover the trunk and older stem joints. The flattened joints, called cladodes, have fine hairs. Their shape ranges from oblong to almost round. Most measure 0.3–0.8 feet (0.10–0.25 metres) long. Some reach about 1 foot (0.30 metres). They grow up to 0.4 feet (0.12 metres) across. Small areoles sit close together on each joint. Yellow glochids fill the upper part of each areole. Below them grow one to three flexible white spines. One spine may reach 0.1 feet (0.03 metres) long.

The flowers have broad yellow petals and white stamens. A red style ends in green stigma lobes. Flowers span about 0.13–0.26 feet (0.04–0.08 metres). The fruit has a scent and a pleasant taste. Its colour may be whitish-yellow or red. Mexican markets sell this fruit as food. These bright flowers and pale bristles mark the plant's appearance.

This cactus grows during summer and is easy to cultivate. It needs soil that drains very well. Sandy or gravelly soil matches its natural growing conditions. Let the soil dry between waterings. Cold, damp conditions make the plant prone to rot. LLIFLE lists USDA zones 7–10, but gives a frost warning. Very dry plants may withstand 19°F (−7°C) or lower. In cultivation, keeping temperatures above freezing helps prevent skin marks. Avoid frost when the air is humid. The plant also withstands very high summer heat.

Stem joints provide a way to grow new plants. They root readily in loose soil with good drainage. Repot in spring when roots outgrow their space. LLIFLE suggests fresh soil about every two years. After repotting, leave the plant unwatered for at least a week. Its edible fruit does not establish the safety of other parts. The supplied species evidence gives no firm toxicity assessment.