Pilosocereus pachycladus aka Blue Columnar Cactus

Pilosocereus pachycladus is a cactus known as blue columnar cactus. It belongs to the cactus family, Cactaceae. Its native range covers northeast Brazil and reaches northern Minas Gerais. It grows in tropical lands with a dry season. Wild plants live in dry woods, coastal woods, and scrub. They grow among rocks and on sandy or stony ground. Some sites have quartz-rich rock exposed at the surface.

This succulent forms upright columns and branches as it grows. In the wild, it can become a tree-like plant. Wild heights range from about 6.6–33 feet [2–10 metres], sometimes more. Plants stay much smaller when grown in pots. RHS lists a cultivated height of 0.3–1.6 feet [0.1–0.5 metres]. It gives the same range for spread. Growth is slow, with maturity listed at five to ten years. The blue-green stems have ribs that run along their length. Small pads called areoles line these ribs. They hold tan spines and fine white hairs.

The plant flowers in summer, with blooms that open at night. The white flowers have a funnel shape. Some have a red tint near their tips. Fruits shaped like figs follow the flowers. The stems keep their colour through the year. Their upright form suits pots where shape is the main feature. RHS lists the plant for homes, patios, greenhouses, and conservatories. In Brazil, people gather wild plants for their wood. They use this wood for local building work.

Give this cactus full sun and a mix that drains well. RHS recommends a standard cactus mix and a sheltered site. Sandy soil with an acid or neutral pH suits it. Keep it at 12°C or warmer throughout the year. In the UK, its hardiness rating is H1B. It can spend summer outdoors in a sheltered spot. Water well in late spring and summer. At other times, keep the mix only slightly damp. The plant can withstand drought, but excess water can cause rot.

RHS reports few disease problems apart from rot caused by overwatering. Mealybugs may attack it, and ants may affect outdoor plants. It needs no pruning. Sow seed in spring at 19–24°C to raise new plants. Useful Tropical Plants records no known food or medicinal uses. It also reports no known hazards, rather than confirmed safety. Its cited 2017 IUCN status is Least Concern. The species is widespread and abundant, with populations in protected areas. Reported threats affect local sites rather than its whole range.