From the Editor: November 2011

November 02, 2011
Written by
You’re not going to trip over the next big thing in plants, but you might strain your neck checking it out.

Plants are no longer firmly rooted in terra firma. Green roofs, plant walls and rooftop vegetable production represent a new wave of greenhouse horticulture.

At present, they’re extremely small segments within the industry, but the growth potential is substantial.

Green roofs have been around since the late 19th century, particularly in Europe, and have only recently gained popularity on this side of the pond. In 2010, for example, the green roof industry in North America grew by some 16 per cent over 2009. Major centres are especially buying into it, in particular, Chicago, which added 600,000 square feet of green roofs on 600 projects in 2010. With about seven million square feet of vegetated roofs, it’s far and away the North American leader.

Two Canadian municipalities – Montreal and Quebec City – cracked the top-10 green roof cities in a survey conducted by Green Roofs for Healthy Cities in 2009.

But Toronto is catching up, thanks to its Green Roof Bylaw that has already resulted in 1.2 million square feet of green space growing well above ground. That city expects those roofs will absorb some 435,000 cubic feet of rainfall each year, water that previously would have drained through the stormwater system. These roofs are helping reduce the urban heat island effect, thereby reducing air conditioning requirements and resulting in annual energy savings of 1.5 million kilowatt-hours of electricity.

Green roofs create new recreational opportunities, and preserve biodiversity in areas previously paved over. Air quality is also improved.

Green walls are also nothing new, but interest is accelerating and Canadians are among those leading the way. NEDLAW Living Walls, located in Breslau, Ontario, recently completed the installation of the largest known active living wall in the United States. The 1,570-plus-square-foot structure is located at Drexel University in Philadelphia. Incorporating the patented NEDLAW Living Walls biofilter system, it is capable of generating between 16,000 and 30,000 cubic feet of “virtual” outside air per minute.

Living walls significantly improve air quality at a fraction of the cost of air conditioning systems.

Montreal’s Lufa Farms Inc., developer of the world’s first commercial-scale rooftop greenhouse, is hoping to open a second – and larger – rooftop vegetable greenhouse next year, with more expected to follow. It recently entered into a co-operative agreement with green industrial-park specialist Le Groupe Montoni of Laval to develop LEED-certified industrial buildings capable of supporting commercial greenhouses. The current Lufa greenhouse is some 31,000 square feet; the next generation will be between 80,000 and 120,000 square feet.

If Lufa is successful, similar operations could find homes across North America, giving a new twist to the concept of urban agriculture by extending the growing season virtually year-round.

Greenhouse horticulture may seem confined by its structures, but new developments are clearly the result of thinking outside the (greenhouse) box and taking plants to new heights.

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