Tips for Growing Pilosocereus Cacti

The blue-skinned P. pachycereus is quite distinctive-looking. Pilosocereus © Medeiros

Pilosocereus is a genus of cacti distributed throughout Mexico, the Caribbean, and Brazil. Containing many species, Pilosocereus includes both cacti that are quite commonly used in cultivation and some that are so rare as to be almost unknown outside botanical sources. The most common houseplant in the genus, though, is P. pachycladus, which large nurseries produce in bulk and sell wholesale. This Brazilian species has a branched form and flowers at night: it is most known, however, for its lovely bright blue skin, which is complemented by its bright yellow spines.

Pilosocereus cacti are mostly shrubby or tree-like, and several other species also have blue skin. Their flowers are shaped like tubes and also often blue, and they grow fleshy fruits. In cultivation, they mostly are grown in glasshouses because of their size and the need for warmth in the winter. Their name derives from the Latin for “hairy cereus” because of their spiny aureoles, many of which have golden spines. Despite its large size, P. pachycladus is a commonly cultivated domestic cactus in tropical areas due to its aesthetic beauty: gardeners with the correct climate and enough space should consider plants from this genus.

Growing Conditions

  • Light: Like most cacti, they need lots and lots of direct sunlight to flourish.
  • Water: Weekly watering should be sufficient for their water needs: they need a solid supply of water during the summer. Make sure not to overwater them, which can cause rot.
  • Temperature: Hot tropical temperatures, ideally around and above seventy degrees.
  • Soil: Pilosocereus plants like a dry soil with some organic material, and good drainage is essential.
  • Fertilizer: Complementing their water with a diluted liquid fertilizer once every few weeks during the growing season will help: use a balanced fertilizer like a 20-20-20.

    Propagation

    The best way to propagate Pilosocereus plants is by cuttings. You can cut off the top of the plant once it’s begun to mature and replant it as the bottom of a new one: this is a good way to produce new plants. Once the top-cuts have rooted, they should flower fairly early in their lives, so cutting off the tops of existing plants is a good way to ensure flowering in your cacti.

    Repotting

    These are tree-like, free-standing cacti that are usually too big to be grown in pots. Cacti in containers do benefit from sporadic repotting, though: lift the plant gently (and make sure to protect your hands), knock away old soil, and replace in a larger pot. Make sure not to water the plant for a few weeks as it gets settled in its new container.

    Varieties

    There are many interesting Pilosocereus cacti beyond just P. pachycladus, which is also listed by some sources as P. azureus. For instance, P. gounellei, also native to Brazil, has an interesting forked branching habit and can grow up to fourteen feet tall, while the “Woolly Torch”, or P. leucocephalus, has dense white hair that grows in between its spines and all over its columns.

    Grower’s Tips

    These are vigorous, fast-growing cacti that need regular water and fertilizer to reach their full potential.

    Make sure to keep them in a warm place in winter and plant them in a place with lots of space, because these columnar cacti will eventually grow to be quite large. Make sure their soil drains well, also—poor drainage is a death sentence to most cacti. P. pachycladus, particularly, is known as an easy, forgiving cactus that can flourish with only minimal help from you, and most tropical gardeners shouldn’t have trouble with them. Keep an eye out for pests like mealybugs and red spider mites and water regularly for best results.