The Key Tree Cactus at Cactus Island

This is the cactus that started it all for me: the Florida Key tree cactus, Pilosocereus robinii.  It is our largest – a green, branching columnar cactus that can reach 33 feet in height with many arms, and what a few of us here call “Florida’s own saguaro”.  Occurring only in the Florida Keys inside the U.S, it also is found in a few spots in Cuba and their coastal keys, reportedly also on a few islands of the northern Bahamas as well. Stems can get 4”+ thick and thicker at support base. Flowers are nocturnal for one night only and have somewhat of a garlic odor. Unlike many others in the genus Pilosocereus, this species doesn’t have areole wool.  The ground on which they grow has a thin sandy soil layer over oolitic limestone.

My journey through Cactaceae began with my surprising discovery at a 1996 Chicago lecture about the Cuban Keys that a number of large cactus species naturally occur in Florida and the Caribbean, not just the desert, and this quite captivated me. Thinking I could go out and buy something so cool at the local plant shop or K-mart to liven up my bright Berwyn, IL apartment window in the frozen gloom of January, I asked my high school bud and prodigious science guy Mark about these, who laughed and informed me that they are at risk of extinction and highly protected.  Just like most native Florida cactus species, these have been pushed to the edge by habitat loss to development, previous poaching, salt intrusion and a future of climate change that doesn’t look good for the Keys.  Fairchild Tropical Botanic Garden has done the science and heavy lifting for many years to prevent the Key tree cactus from being lost forever.  The thought remained on the back burner for years as I built my career as an artist, but it inspired me to try my hand at growing various popular varieties in my kitchen windows as I moved over the years. 

Seeing the three-story high Peruvian apple cactus candelabras (non-native) around Fort Myers on previous Christmas visits again fired up my interest in Florida’s native cacti.  In 2014 I moved to Florida and wasted no time learning about Cactaceae while experimenting with what would grow well in North and South Florida.  My initial successes in germinating and retaining seedlings led to refinement of process, innovative combined techniques, optimum soil mixes and an armada of robust cacti as I started and learned to run a cactus farm.  

One of the highlight specialties of Cactus Island is the cultivation of native and endemic Florida cacti, and I began with both species of shrubby coastal prickly apple cactus in the genus Harrisia, seeds of which I ethically acquired from reputable major seed companies.  Those are now in full cultivation here with large plants that have fruit of their own.  Unexpectedly, in April and June of 2022 the Key tree cactus came into my stewardship from two sources and two distinct populations:  two P. robinii plants of the Lower Matecumbe Key population given to me by a conservator and a P. robinii fruit of the Big Pine Key population from a private landowner there who saw my blog, liked what I’m doing and contacted me.  He also set me up with a fruit of a distinctly different Big Pine Key Harrisia with huge yellow fruit, short white needles and a sprawling, decumbent tendency.  Seed of both germinated prolifically, and now I have rows of fast-growing endemic Florida cactus.  A few trays of plants will be headed back to the landowner for planting.  He’d also sent me home with rooted cuttings of Opuntia abjecta and Consolea corallicola to add to the Opuntia keyensis, all of which grew into prime form for next spring’s anticipated completion of the Caribbean and Florida stone cactus cairn gardens. 

Given the integrity of my plant material sources, I am clear with FWC to have these and the other critically endangered cacti, but I can only sell them in Florida.  The idea that this landowner and I share is to get them into responsible cultivation.  I am selective about who I sell them to and prefer that they go to other serious, committed cactus growers here who will take care of them, preserve their data, protect from hybridization and keep in touch in the event that they bloom.  Fellow Florida Native Plant Society members, a few cactus botanists and smaller botanical gardens that didn’t yet have these is a nice start.

Cactus Island is also participating in a project along with a handful of other growers to propagate over 40 threatened Brazilian Pilosocereus species and subspecies from seed.  The plan has been to return some of the resulting plants and controlled-pollination seeds into the cactus conservation network and eventually bring these species into cultivation.  I maintain a standard of taxonomic accuracy and pedigree without accidental or deliberate hybridization; flowers, fruit and seed are carefully managed.  Fruit that sets without known parentage is excised and composted; our 8b/9a sandhills ecology is conveniently not a place where Zone 10a plants can get a toehold. Being 151ft above sea level is also a plus.