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| Hydroponic Rooftop Gardening Generally used for growing vegetables, hydroponic rooftop gardens are a low-cost alternative to living roofs. In hydroponic gardens, plant roots are provided with liquid nutrients thus eliminating the need for heavier organic materials. In some cases a lightweight substrate, such as perlite combined with inert organic materials, is substituted. The hydroponic “cells” are then added to an existing roof structure. Since the cells generally add 9-16psf(1) (pounds per square foot), in most cases, no structural retrofitting is required. A study of hydroponic rooftop gardening found that a hydroponic rooftop garden can produce 4psf. of vegetables annually, compared to 2.5psf associated with typical field conditions. (1) This study shows that hydroponic rooftop gardening can be an effective way of providing more fresh vegetables locally, relieving transportation cost, pollution, and product degradation and loss due to transport conditions. The growing medium is ideal for its low weight and high nutrient content. Appropriate plants include (but are not limited to): salad greens, most summer & winter vegetables and herbs. Planting methods may vary. Generally seedlings are transplanted into the hydroponic cells where they have unrestricted access to the vital nutrients provided by the growing system. In most cases a "flood and drain" technique is used to provide the nutrient solution. A storage tank is set up with a pump to "flood" the tank. The growing container is constructed with a drain approx. one inch above the base. The nutrient solution is then allowed to drain (possibly gravity fed) back into the storage tank for recirculation. (1) (1) "Tapping the potential of Urban Rooftops Rooftop Resources Neighborhood Assessment" Study by Bay Localize. Oakland, Ca |
Sonoma County Rooftop Resource Inc.