Gardens everywhere, even city rooftops

Rooftop gardening is possible with a little preparation.

Rooftop gardening is practical with a little preparation. Photo: Peter Blanchard via Flickr.

Transition means locally grown food, among many other things.  As the fuel that powers our vehicles continues to increase in price, the cost of shipping food hundreds of miles will become prohibitively expensive.

That means our awareness of the origins of our food will be on the increase; it only makes sense. A local farmers’ market? Great idea. Community Supported Agriculture? You’ll have enough to share with friends. Grow your own? There’s never been a better time, especially for city dwellers.

And if space is an issue, start thinking in terms of space you may have forgotten you have: your roof.  Rooftop gardening is the urban gardener’s new best friend.  When you plant a garden on your roof, you can:

  • Improve air quality and reduce atmospheric CO2
  • Reduce stormwater runoff
  • Increase habitat for birds and insects
  • Insulate your home, thereby reducing heating and cooling costs
  • Increase the life of your roof
  • Increase the ready availability of naturally beautiful surroundings

There are a number of ways you can carry through on this idea: planting a garden which, first and foremost, is a retreat where you use and improve your green thumb—a place for beautiful flowers, a winding path, maybe even a small fountain; designing a multi-use garden where you can experiment with cultivating both flowers and vegetables, vertical gardening, or possibly even animal husbandry; or devoting your rooftop space solely to the growing of food.

Once you’ve imagined your rooftop garden to the point of listing the plants you’d like to grow, there are a number of practical measures you’ll need to consider before making your dream a reality.

Plan ahead

Does your city, town or county allow rooftop gardens? Assuming yes, a permit, or permits, may well be required in order for the city to assure itself that your project is being undertaken in such a way that your roof will neither spring leaks, nor collapse from the new load it’s now supporting. In order to avoid these negative possibilities, get a contractor involved right from the outset. Don’t forget, your roof must not only support the weight of your garden, it must also be able to support the water weight your garden will absorb, along with the weight of the people who plan to visit your garden. This is no time for guesswork!  Get an expert involved.

Perhaps at this point you’re saying, “Geez, I didn’t know it would get so involved. I just want to putter around with my plants. Who has the money for all that?”

If the answer to that question is “Not me,” then consider this alternative: container gardening. Lightweight plastic or wood containers, filled with a lightweight planting medium, can provide you with lots of gardening satisfaction without all the hassle. If aesthetics are not a primary consideration, think about using five-gallon buckets. They can accommodate good-sized plants, and are easy to move. Smaller buckets can provide the same convenience for smaller veggies or flowers.

Regardless of whether you’re thinking big or small, you will need to water the plants you grow.  You’re going to carry water up to the roof from the spigot on the side of the house at ground level?  Don’t even think about it. When your plant collection grows, as it inevitably will, you will tire of this arrangement well before the summer comes to an end. A licensed plumber will be able to help you figure out how the water will make its way to the roof. If this is out of his or her league, you will need to find an irrigation contractor.

Make sure your rooftop garden can take all the weight of the plants, plus any other materials and water absorption.

Make sure your rooftop garden can take all the weight of the plants, plus any other materials and water absorption. Photo: Peter Blanchard via Flickr.

As for drainage, your gutters will probably be fine, though they will need to be shielded with screens in order to prevent clogging.  This is especially true during heavy downpours, when soil erosion becomes a factor.  Any number of things collect on rooftops, including leaves, twigs, nuts, and acorns, all of which will attempt to set up housekeeping in your gutters unless you employ barriers to keep them out.

If, instead of a single-family house, you live in an apartment or condominium many stories above the ground, wind is going to have to be taken into consideration. After all, the roof is even higher up than you are. Believe it or not, wind speed doubles for every ten stories.  If you live in a twenty or thirty story building, and wind speed on the ground is 13 miles an hour, that thirty story apartment complex “enjoys” wind speeds of 52 miles an hour on its roof. Buildings taller than ten stories and/or buildings in a windy locale probably are not good sites for rooftop gardens.

You are now at the point of having verified that your roof can support the weight of a rooftop garden, and you have accepted bids for all the aspects of building the garden and infrastructure that you intend to contract out. There is still the matter of designing, and planting, your garden. Among the layers you’ll lay down before you spread your growing medium are a waterproof membrane, a root barrier, an insulation layer, a drainage layer, and a filter mat. Once you’ve got that filter mat in place, you know you’re finally getting close to the fun part.  As with any building project, be sure you lay a solid foundation. With that part out of the way, you can look forward to enjoying your rooftop garden for many years to come.

In the Northern hemisphere we’re just moving into the cold season, a perfect time to do the research and planning that will help you be ready to enact new gardening plans next spring. Want to learn more?  Here are some excellent sources of information about rooftop gardening:



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