The Cactus Roof

Horticulturist's Tour

Listen to NFATC Horticulturist Darren DeStefano talk about how budget and time constraints forced him to get creative with the Cactus Roof. 

I really wanted to create a green roof on this space, but I was never able to derive the budget or convince anyone that it was a great idea. So, I set about trying to do it myself, by being creative.

So, in taking on the roof of the Cafeteria, I was reaching the end of my contract tenure on the site, and I had developed a relationship with Dominique Bain, who was with the Denver Botanic Garden(s). And we had talked for years about doing cactus roofs—roofs that have almost no maintenance requirement and no alteration from their current condition. The concept was to use cacti and to spread them out like you find them in their natural environment, and to actually use a whole bunch of different species that come from the high desert around Denver and Utah—Colorado and Utah—and see how well they would perform in Washington.

(Scroll to follow along with the audio.) 

All of these plants were sent to me in a box. They were just cacti where pads had been just broken off, and then they were allowed to callus, and then they were shipped to me in Washington. And I got some bags of pea gravel and went out on the roof and poured around the pea gravel and slid in these cactus pieces.

After that, it was really just time and Mother Nature. See who was going to survive and if this concept had any merit. And in order to give it more of that desert feel, I thought I would incorporate a bunch of woodfall. So, I went around campus and gathered up different branches and sticks, and I hauled them up on the roof with ropes and I created a little scene out of it. 

I really only saw the cactus for about six months, and then I was gone for two years. And when I came back, perhaps no garden had flourished as much under the sheer neglect of my absence as the cactus. It was really remarkable to see how much they’d grown and really how attractive the planting actually was, and how unusual. You know, that’s what I really like about it—is its novelty.

It’s probably the largest collection of cactus for a great distance. I mean, there are Cylindropuntia and Opuntia; there’s agaves and Hesperaloes. I mean, it is a fascinating collection of these species, and they produce these really dramatic flowers. I mean, when they flower, when the desert blooms, it really is spectacular to behold.

And you get the added benefit that they all produce fruit. Most of them are prickly pear, and they produce this really attractive fruit that’s quite persistent and is ornamental in its own right. I also really appreciate how the needles catch the light—that’s truly the beauty of a cactus. It’s actually in how the needle—the spine—can capture the incoming light and produce a halo around the plant. And they almost look, you know, like they’re a vision from a distance.  

In reality, it was a crazy idea, but it was executed with nickels and dimes. It was something that was really off the wall and had no precedent for. And it was a real test balloon to put it out there and be like, 'Hey, if you’ve got a very low budget and you’ve got a roof that you do not have the ability to get the ballast off and convert to a green roof, is there a way to still get something out of it?'

And while it doesn’t have the same ecological benefit as a true green roof where the sponge absorbs all of the rainwater, you get this aesthetic benefit. And that aesthetic benefit can be significant. I mean, if you’re in a situation where you’re looking out that window and there’s nothing but a kind of brutal gray gravel, that doesn’t pick you up in any way. Whereas walking down that corridor and looking out the window and watching this desert scene kind of pass you by—it’s quirky.