How to Start a Green Roof Garden- Garden-lovers without backyards, go vertical!

How to Start a Green Roof Garden

Garden-lovers without backyards, go vertical!

Such is the cry of a Park Slope resident who recently showed a crowd how to start a green roof garden. Since starting a roof garden is a bit more complicated than planting on the ground, it took us step by step through the process, including how to set it up, what to grow, and how to maintain it.

A green roof generally means a

carpeting of plants on a roof, which improves the energy performance of buildings, and reduces storm water runoff. Though many urban dwellers have flowerpots or container gardens on their roofs, these aren't providing the energy savings that green roofs do.

So set out to create a vegetable garden that would provide some of those benefits. While the garden far from carpets roof, it does sit right against the roof membrane, helping to insulate house, while providing fresh food for family.

If you'd like to start a green roof garden of your own, here are some things that you might want to take into consideration:

Safety First and foremost, you want your garden to be safe. This isn't just about protecting those on the roof from falling off. Since roofs are generally windy places, you'll also want to protect passerbys from falling tools. So install fencing and securely tie down all equipment. Consult your local department of buildings for any necessary permits and regulations about fence height.

Weight Wet soil is heavy. So too is a foot of wet snow on top of that soil. So you'll want to figure out the sustainable weight load of your roof (consult a structural engineer), as too much load in the wrong places can cause structural damage. In most cases, you'll need to use a planting medium instead of soil.

For wood roof, use a mix of 15% stalite permatil, 15% vermiculite, 25% compost, and 45% stalite, (available through gardening centers.) Since the nutrients have been consumed, the compost gets renewed at the start of every season, but otherwise the estimates will not need to replace this. 

Containers You'll need a container that is lightweight, but allows drainage. For maximum energy benefits, it should sit flat against the roof. It uses a modular planting system designed for green roofs made by Green Grid. So that the plant roots don't burrow into the roof membrane, this lines the recycled-plastic trays with a fabric weed block. You muse have seen also seen roof gardens created in wading pools, feed sacks, and even recycled tires.

Watering In the hottest months, you'll need to be watering daily. So solve the problem by running a garden hose up the side of the building, and attaching it to drip lines and a timer system. This allows to go away for several days at a time without worrying about the plants dying.

Plants Finally, what can you grow up there? Part of it depends on your available weight load. You can grow most of the vegetables in an 8" deep tray, which will figure to weigh 24 lbs/sq foot when damp, and 28 lbs/sq foot when soaking wet. Even still, not everything does as well as it would on the ground. 

You can conclude that the planting medium is too gravely and perhaps not deep enough for root vegetables. But the breadth of the successful vegetables is impressive. We'd love to have that many things ripe for the picking on our roof, wouldn't you?

- by Nina Callaway