I've walked past these buildings and they look <i>nice</i>, but I was/am not so optimistic about the maintenance required when the buildings are 20, 30+ years old. From the article:<p>> Periodically, a group of mountaineering arborists lowers themselves from the roofs of the two towers to tend to the plants, checking their health, and pruning or replacing them as needed.<p>Are these <i>mountaineering arborists</i> volunteering for the fun of it? Paid by the building management? Residents? If volunteers, it sounds like a fun activity but quite unsustainable for more than a handful of buildings. If paid (now or in the future), I'm quite curious what the average cost is and what the contingencies are for a lapse in maintenance due to change of ownership, rising cost leading to longer maintenance interval, etc. Maintaining the greenery is one aspect, but so is maintaining the concrete holding it up.<p>Despite my lack of optimism I do find it interesting to explore. Sometimes a few... mildly bourgeois... early demonstrations do provide the inspiration and requisite practical experience to get things rolling.