Rooftop gardens are a great alternative to having a yard and garden or having a balcony filled with pots. In many cases a rooftop garden insulates the roof and helps the roof reduce storm run-off that can damage siding and gutters. Rooftops are often left bare and are a big waste of space. A green roof can be efficient and produce food for the family.
Local Laws and Permissions.
Many urban municipalities have laws or ordinances that might apply to rooftop gardens. Always check with city hall before installing a rooftop garden. Those that rent or have home owner associations should also check to make sure there are no regulations on gardening on a rooftop.
Anyone starting a rooftop garden needs to get an opinion from an architect or building contractor before they do anything including purchasing materials to make the rooftop garden. The roof needs to be inspected to see if it will support a garden. A rooftop garden adds a great deal of weight to the building and some rooftops are not designed to support all that weight.
Weight Concerns and Weight Saving Techniques.
Rooftop gardens never use regular garden soil mainly because it contains clay and is very heavy especially when wet. Not only does the roof have to hold up soil, but also the plants, people, and any containers that might be used. Ways to keep weight down is to use lightweight potting soil, plastic/foam/fiberglass containers and instead of using gravel under the soil for drainage purposes – use Styrofoam peanuts that are very light and airy.
Creating the Garden!
Low, flat garden containers made specifically for rooftop gardens are available for purchase. They are plastic or fiberglass and sit right on the roof. The potting medium goes inside and this prevents roots from penetrating the roof membrane, which can cause leaking inside.
It is probably a good idea to use fabric weed block inside each container and then put the potting medium in. The containers need to be at least 8 inches high to be effective in growing above the ground crops and might need to be a little deeper for root crops.
Other things that can create a rooftop garden are kid’s plastic wading pools and old tires. Grow potatoes in tires starting with two stacked on top of each other and keep adding planting medium and another tire as the vines grow.
Most herbs are suitable for a rooftop garden. Vegetables that do well include lettuce, peas, bush and pole beans, zucchini, summer squash, kale, spinach, peppers, cherry tomatoes and greens. Tomatoes grow somewhat well but need deeper than 8 inches and should probably be grown in 12-inch high pots. Carrots and melons don’t do very well because of growth habits.
Wind, Rain, and Sunlight.
The wind is much more prevalent on a roof than it is on the ground and wind pulls moisture from soil. It can also blow over taller plants and create havoc. Reed or bamboo screens and trellises can protect plants from high winds. Be careful with your lightweight pots because the wind can easily topple them over. It is a good idea to secure them to railings or permanent fixtures on the roof.
Sunlight generally isn’t a problem on the roof because there is nothing to stop it from beating down day after day. This can cause a different problem of sunburning and drying out plants. A shade cloth or screens might be necessary to protect plants from the sun. A retractable awning works very well and can be raised and lowered as needed.
Do not depend on just rain as a water source to a rooftop garden. There needs to be some access in a spigot and hose or something to deliver water to the garden. All containers with soil in them need to be able to drain and the rooftop needs to have a waterproof membrane of some sort to protect the building from leaks.
One easiest way to get water to the roof is to run a hose up the side of the building from a spigot and attach it to soaker hoses running through the containers. Set it on a timer and the garden will be watered at the same time every day.
A rooftop garden is a wonderful alternative for those living in an urban setting. However, safety is of the utmost importance. The roof needs to be able to support the extra weight and it also needs to be waterproofed so no leaks break forth.
A type of fence is often needed so that nothing can blow off the roof and hit passer byes or vehicles beneath. A water source, shade and wind breaks are also necessary. The rooftop garden can provide food and enjoyment for years to come when done properly.