image via Thomas Balsley Associates

I saw the post in The Dirt recently and recall previous posts on Metropolis and a mention in Forbes regarding NY urban gardenening about Thomas Balsley’s rooftop monoculture forest at 101 Warren Street in Manhatten and I have to say that I’m conflicted about this project.

I’m surprised there isn’t more criticism on this, especially on the line from the Metropolis article, “The goal was to achieve a tranquil place rather than a pretty or functional one.” Wow, I could never imagine saying something like that and getting away with it. I realize that as professionals we are always happy when a green roof is built but shouldn’t there still be dialogue? What do people out there think of this one?

image via Thomas Balsley Associates

First, I’d like to address the simple fact that this project is built at all is quite the accomplishment. For an owner to decide that hauling up over a hundred large 25 foot tall Austrian Pines via crane onto the rooftop and allowing a 54″ soil depth down into the roof (or does this number include the raised/mounded portion above the roof?) is worth the money and the effort…is huge.

While green roofs are popular these days, they are still costly and clients are not always willing to fork out the money for height, no matter how much more we say the value of their property will increase. But with more and more examples being built out there with trees that we are able to point to as designers and provide as successful, working examples to our clients, the better they can understand the benefits versus the cost.

image via Thomas Balsley Associates

image via metropolis

Although, I can’t help but wonder if 54″ is sufficient for trees that could eventually reach 60 feet in height (although perhaps the space will confine their growth and given that this is not a native forest environment, they’ll probably only get to 40′ yet that is still large) and whether trees of that size are even appropriate for rooftop applications, not only for weight purposes but also wind. When I visited the Washington Mutual Green Roof earlier this year, they had some small Shore Pines, maybe 15′ feet tall at the most, that were tied down with several cables all around the trunk. Granted the pines at this mixed-used tower in Manhattan are only planted 2 stories up on the towers podium (this according to tbany.com, although Metropolis says 5 stories up), whereas the trees on the WAMU tower were much higher but I still wonder if wind is at all a factor (wind tunnel effect?) and what kind of precautions need to be taken for stabilization or is the soil depth sufficient for trees of this size? Perhaps it might seem like a silly question but a wind study was done for one project I was working on with a green roof and eventhough the roof space was just a couple stories above the ground we found the wind to actually be quite a significant issue. This is different everywhere, but it was one of the first questions that came to my mind when reading about large trees.

image via Lisa Town

Balsley mentions that he wanted to create a “monoculture of evergreens to emulate the northern forests” and are also an effort to avoid the typical blankets of sedum and highly manicured containers. While large expanses of sedums are a great option for achieving the benefits of a green roof for those that only have 6 inches or less to work with, they are an extensive type of roof and different from an intensive-style roof garden. But a roof garden also doesn’t have to be a high maintenance endeavor with over manicured pots, as Balsley mentions. In fact, I thought the typical point of a roof garden was to create something that was of a benefit to the environment as well as residents and not a maintenance hog? This seems like an over generalization on Balsley’s part in trying to justify the design. In fact the WAMU green roof is a beautiful and successful example of creating a natural and artistic landscape in a rooftop setting and includes native vegetation and no manicured pots.

image via Thomas Balsley Associates

Balsley states that the forest is “a different idea of what an amenity should be. It’s not always something you can use.” And this statement is fine (although again, quite bold) in one sense because I agree that the ability to look out into or over vegetation still provides a great amenity. Afterall, wouldn’t you rather look out over vegetation as opposed to other buildings or streets?

However, while it can be fine, albeit unfortunate, that people can’t “use” a roof garden it seems to me like there should be a reason for this other than the designer just not wanting people to. One great reason could be environmental or habitat benefits. Pine trees are excellent habitat for insects and birds and allow for hiding and perching opportunities. While I do like the way it looks to have these pine trees standing like artistic columns in waving mounds surrounded by corten and contrasting river-washed rock it does seem rather unfriendly in some areas and I think it could’ve been so simple to provide maximum habitat benefits without compromising the designer’s vision.

image via metropolis

The main thing missing for good habitat is a food source. I realize the point was for a monoculture, hence the choice of Mugo pines as the shrub base for the trees, but if a different shrub or groundcover were chosen that provided flowers and berries, then suddenly there is a food source and that changes the trees from simple perching areas to also providing nesting opportunities as birds want to nest near a food source. The monoculture of trees would still exist and the ground plane could be it’s own monoculture at the trunk base, thus the overall vision would be unchanged yet the environmental benefits would’ve more then doubled just from one simple plant choice revision.

So with all that I ask, does a monoculture of mature pine trees belong on a green roof? Should design vision take precendence over usability or environmental impact? Does one need to be able to “use” a green roof in order to achieve the same benefits? It will be really interesting to see how this forest does in fact grow and mature over the years and how the community and professional view towards the garden grows and changes along with it.