Sustainability in urban horticulture is loaded with contradictions. Some of the projects taking place, and often the money that goes into them, makes it seem as if many of the precepts of sustainable urban landscapes are anything but. You’ve got solar panels covering farms (and gardens) and farms and gardens going on roofs. Plants hanging on walls like drapes, dependant on pumps moving water and carefully calculated chemical brews flowing through them like a bloodstream. Repurposed warehouses packed with state of the art lighting systems subsidized by foundations producing crops of boutique baby greens to be sold at high end restaurants. Yeah, maybe, anything but. But…

But sometimes we forget that sustainability is a three legged stool. Alphabetically, the first of the three is economic, and I think we can all agree that on an economic basis, many, but not all, urban horticulture projects don’t make a lot of sense. The second leg is environment. Again, some of these projects do, some don’t. But it is the third leg, which, although often overlooked, might be the most important, and that is social. After all, we’re all people and these are urban projects. So maybe our first goal in urban horticulture should be to use plants to benefit people and, to extrapolate from there, if a project is also environmentally and economically successful, then there is the hoped for bit we wanted from horticulture in the first place. 

I recently heard a wonderful talk by Neil Hendrickson about the memorial oaks at the 9/11 Memorial in New York. Long story short, nothing about the planning of that project, the design, the planting, nor the maintenance makes any economic or environmental sense. It just doesn’t. Socially, however, it wows. If you haven’t visited, you must. And if you do, expect to be profoundly moved by the reflecting pools, the walls etched with every name, and the surrounding planting of over 400 swamp white oaks. With these elements, the Memorial does exactly what it was intended to do, and that is to heal the living and honor the dead.


The second part of Neil’s talk took an unexpected turn because it found a different story to tell from the same tragic event. And that was about “the Survivor Tree.”

The Survivor Tree is a tree that was growing in the WTC plaza, and, although badly burned and mangled, it somehow survived the towers falling around it. At some point it was pulled from the wreckage and the NYC Department of Parks and Recreation nursed it back to health. Replanted at the Memorial in 2010, it is thriving today and is an integral part of the visitor experience, symbolizing perseverance and rebirth.

The Survivor Tree.

And of course it is a Callery Pear. I say “of course” because what else could survive what it survived? And “of course” as an ironic aside, because, horticulturally, it muddies the sustainable urban horticulture waters like everything else. And, I will venture, like nothing else!

Callery pears are a scourge. The adaptability that in part made them the number one choice for urban and suburban usage combined with their unparalleled fecundity has made them one of our worst invasive plants. Ubiquitous in landscapes, they are now abundant along roadsides, open fields, and empty lots. Some states have banned their sale. While this is a great, if belated, move, it is mostly symbolic. The Callery pear cat is out of the bag and there is nothing anyone can do to put it back in.

So the irony of the soulful and whole-hearted effort that some very dedicated people put forth to preserve and replant a Callery pear was not lost on a horticultural audience and I heard the occasional gasp and even some scoffing laughter as Neil earnestly continued.  

But the story soon took a further turn as Neil told us about a group that is sharing vegetatively propagated cuttings of the Survivor Tree with fire stations and others around the country who are in some other way connected to the 9/11 tragedy. Waves of gasps and scoffing swirled. What? A banned species, a species many had come to loathe, being deliberately spread around the country ran entirely counter to everything we’ve learned the past few decades and against horticulture’s yawning change in direction.    

But keep in mind here what many in the audience did not. That in the grand scheme of things, at a time where pears are already everywhere, that a few hundred Survivor Tree saplings entering the world will essentially have no affect on it. Essentially nil. Nevertheless, the gut reaction of many in the audience was to openly react to the irony of it all and what it symbolized. 

And I get that. From an environmental perspective, it is absurd that any effort is going into propagating and sharing one of the most invasive plants we face today, and I too want to shout that we don’t need any more Callery pears anywhere. But, on the other hand, there’s nothing ironic about the feelings those most affected by the events of 9/11 have towards the one tangible, living thing that still survives from that place on that day. And what it symbolizes is very heavy indeed. 

And so green walls bring life to urban canyons and green roofs turn acres of gravel wasteland into green space. Urban farms grow produce where it wasn’t before. For the people. Sometimes, such projects are worth the money. Sometimes not. Sometimes they make the environment better, sometimes I just don’t know. But there is that third leg and it’s an integral part of the sustainability stool. Balance seems to be the key.