Pilosocereus royenii (2019)

By Pat Mahon (October 2019)

Pilosocereus royenii grows within the karst topography on Grand Cayman. Photo by Pat Mahon.

While in the Caribbean, we made an incredibly important stop to Grand Cayman, an island located just south of Cuba. Botanist George Proctor, author of Flora of the Cayman Islands, proclaimed that there are more endemic species found in the Cayman Islands than in the Galapagos. This is likely due to the isolation of the islands in closer proximity to other islands, and very tough karst conditions.

Having met up with the head of horticulture at the Queen Elizabeth II Botanic Park, we viewed some of the endemic orchids and succulents of the island. We drove the car to a very sketchy part of the island where the road was being widened, cutting into the woods. It looked like a thicket of weedy bushes and trees, but to my surprise, the dense vegetation was hiding an incredible treasure trove of species.

The karst locale was riddled with sinkholes, and walking on the fossilized coral ground was like walking in high heels four sizes too large. Navigating into this area was very difficult, and the low light meant the maximum distance you could see was about 20 feet. Respecting the epiphytic life on the trees and rare plants beneath us made movement very, very slow.

We saw endemic orchids, an endemic species of Agave and several species of cacti. I accidentally discovered a new species of orchid, so this was indeed a treasure trove of diversity. Though most of my interaction was with an itchy and aggravating epiphytic cactus, we will focus on the less-annoying native Pilosocereus royenii.

Large P. royenii in its natural habitat in Puerto Rico. The plant is endemic to the Caribbean. Photo from Wikipedia by Xemenendura.

There in the deep shade, in high humidity, growing on sharp, jagged rocks was a small dildo cactus. Hey, I did not make up the name; it is commonly called this by the islanders. It is not a particularly attractive species, but it seems to be a very rugged species that does not follow the rules of what cacti tend to like.

P. royenii is considered the most common cactus species within the Caribbean, ranging from the Yucatan to the Bahamas, south down into the Antilles. The flowers are white and resemble many of the other members of the Cereeae tribe.

Although this species is impractical for growing in a small greenhouse, it is a great learning example. Despite what we believe we know about plants, sometimes they will grow in conditions that do not seem to fit their descriptions. Do not be afraid to experiment!

Cayman Flora –
Llifle Encyclopedia of Cacti –