Skilled gardeners, having mastered the trickiest entanglement of spindly, climbing bougainvillea vines among other hard to grow species, are unearthing a new challenge in the form the of rooftop gardening. All across the world, novice gardeners as well as those with finely pruned green thumbs are attacking their rooftops with a renewed sense of purpose. In densely populated residential areas, city dwellers are planting up high in an attempt to reconnect with nature and to produce a few homegrown edibles to counteract the ever-increasing cost of buying food. Yet, you do not have to feel packed like sardines in a tin can to enjoy the benefits of an added layer of insulation and shade or to appreciate the formation of a new habitat for a variety of birds and butterflies to flutter about. Many less urban areas are taking to planting green roofs as well.
Major innovations in engineering and technology have allowed gardens to prosper in the most unlikely of places, and leading metropolitan areas are beginning to encourage and implement standards for planting on the rooftops of private, commercial, and governmental buildings. Both Toronto and Switzerland recently passed bylaws that require the implementation of rooftop gardens (or green roofs) on all new residential and commercial buildings. Basically, one half of the roof coverage on multi-unit residential dwelling, schools, non-profit housing, and industrial buildings must be covered in green.
Most famously, the city of Chicago introduced plans to construct a massive rooftop garden atop City Hall to help combat the city’s intense heat island effect. Urban heat islands are common in most highly developed urban centers, and the result is a substantial and ultimately costly increase in temperature compared to less developed, more rural areas. Encompassing over 38,000 square-feet of rooftop and consisting of 20,000 plants of more than 100 species, Chicago’s City Hall green roof has become a shining example of the benefits of planting above ground.
In addition to the sheer beauty of the spectacle, energy costs have been reduced by an average of $5,000 per year, and the garden is able to absorb 75% of storm water runoff while simultaneously improving the overall air quality. Nine years later, the seemingly risky investment initiated by Mayor Richard M. Daley has paid off both locally, to reduce government expenses and increase employee morale, as well as nationally, to illustrate the untapped potential for creating greener cities throughout the United States. Brad Pitt’s Make it Right foundation has been a vocal proponent of green initiatives locally, encouraging participating architects and designers to incorporate green roof features into the new homes being built in New Orleans’ Ninth Ward. Especially relevant for our area is the absorption of storm water runoff that rooftop gardens provide. The less water running into the streets and down the drains, the less water local residents will have to pay to pump out of low lying, flood prone areas.
The easiest option for someone looking to start a minimal green roof project is to commit to either an intensive garden or a strictly container garden. In the language of green roofs, a garden can either be extensive and include between one and five feet of soil spread out along the surface, or it can be intensive with only one to five inches of soil. Adding an extensive garden to a rooftop is a larger investment since the structure may need to be reinforced to carry the larger load. Wet soil, heavy containers, and human foot traffic are all considerations that must be accounted for prior to planting. Even though the existing roof surface may appear water tight, it is always a good idea to place an additional membrane under containers or across the entire surface. Lastly, when selecting plants for the garden, try to find varieties that work well in your area with the least amount of upkeep and ones that can withstand direct sunlight and uninhibited wind gusts.
Planting up high definitely presents its own set of unique challenges, but with every passing day, more research is conducted and more helpful tips and techniques are developed. And as more and more communities begin to legally require these types of green initiatives, qualified professionals are popping up who can assist in consulting with customers about their green roofs or, in larger projects, can design and construct the garden using the latest innovations in materials and research to ensure that the project is successful in all of its aims. Inevitably, the goal of rooftop gardens is simple. Beyond all of the scientific findings and progressive environmental benefits associated with green roofs, the basic idea is to replace the green space destroyed by a footprint of a building so that an overall balance between man and nature is maintained and preserved for generations to come. And from that bird’s eye perspective, it makes a whole lot of sense, right?