You’ve enjoyed your visits to your local farmer’s market, as you discovered an enticing cornucopia of vegetables. You found red, yellow, and even pink tomatoes. You couldn’t decide between bright yellow summer squash or rich dark green zucchini, so you bought them both. While it was satisfying to support your local farmers, you really want to grow your own vegetable bounty. If you live in an urban environment, or an area with little horizontal gardening land, you’ve thought that growing a vegetable garden is simply not possible. You’ll be pleasantly surprised to learn that a rooftop garden, bursting with delightfully fresh vegetables, might be another option. Careful preparation will give your garden a great chance of success.
Roof weight tolerance
Before you plan your garden’s layout, determine if your home’s roof can support the garden’s weight. This largely depends on the soil depth. For example, an extensive green roof uses 1 to 7 inches of soil, with a weight load of up to 15 pounds per square foot. In contrast, an intensive green roof needs 8 inches to 4 feet of soil, drastically increasing the roof load to 80 to 150 pounds per square foot. An intensive green roof also requires more maintenance as it supports a heavier, thicker vegetation load. Hire a structural engineer to determine if your roof can safely support a substantial garden. If not, consider a lighter-weight garden on top of your storage shed, and brace this smaller roof with strategically placed wooden supports.
Green roof components
Assuming your roof can handle the garden’s weight, focus on protecting your home from water intrusion. Begin with a waterproof membrane, along with a layer that protects against root damage. Next, a drainage layer sends the water to your garden rather than into your home. A specially formulated fabric keeps your garden soil from mixing with drainage water. A lightweight garden soil keeps the roof load down.
Choosing your vegetables
Selecting your vegetable seeds will likely be the most enjoyable part of your garden planning. Before you purchase dozens of seed packets from retail outlets and seed catalogs, realize your region’s growing conditions won’t be suitable for certain vegetables. Other vegetables, such as cabbage, cauliflower, and summer and winter squash, require lots of spacing between plants and/or rows. Unless your rooftop garden encompasses an entire city block, these space-hogging vegetables aren’t the best choice. For recommendations on vegetables that thrive in small-space gardens, contact your county’s Cooperative Extension office: http://www.csrees.usda.gov/Extension/.
While your rooftop garden requires regular watering, weeding, and fertilizing, you (and your family and friends) will soon enjoy the garden’s rewards. Besides fresh produce, your mini-ecosystem will likely attract colorful butterflies and hummingbirds, along with beneficial bees that pollinate your crops. Your green roof also serves as insulation, helping to cool your home in hot weather and keeping it warmer in the winter. Finally, tending your vegetable plants and seeing the fruits of your labors might provide you with a sense of calm and satisfaction.