Have You Heard About Green Roofs?

There was a program, I think on The Discovery Channel (should've written it down, but didn't think of it at the time - obviously!) about two months ago about the concept of greening up roof tops.  Some countries in Europe even mandate new buildings have green roofs! This program was filmed in an urban setting, with lots of apartment and office buildings that had flat, tar paper roofs at one time.  Many of these roofs had been turned into gardens at the edge of the sky, with a variety of plantlife from mosses to wildflowers, and almost anything in between.  The program made some very strong points in favor of this type of gardening because of it's impact on the environment:

• reducing temperature of the city
• weather protection for the roof
• reducing energy costs
• potential flood reduction
• providing habitat for wildlife - birds, butterflies and bugs
• cleaner air
• providing food

The radiant heat generated from black, heat absorbent tar paper roof tops has been shown to increase the overall temperature in cities.  A green roof can reduce that temperature by reducing the heat absorbency of the roof, and at the same time can protect your roof from weather and ultra-violet light damage.  This latter, over time, damages a roof top which can cause leaks and replacement costs. 

Rain is absorbed into and by the plantlife and  medium, to be released slowly through evaporation (an additional cooling factor).  This reduces the chances of flooding in heaving rain.  Additionally,  the photosynthesis of the plant life removes carbon dioxide from the atmosphere!  Imagine if green roofs were required in the U.S.!  What an impact it could make on our carbon footprint!

Green roofs also provide insulation to the room(s) below them, keeping it/them cooler in hot weather and warmer in cold.  Clearly the insulating nature of green roofs will reduce energy consumption and thereby save on the costs of heating and cooling.

So now I bet, if you have any flat surfaces exposed to the outdoors, whether roof, deck, shed or outbuilding, you're probably thinking that having one of your own is a good idea!  If you like the idea of having a green roof and have a large area to work on, you'll want to enlist the help of a structural engineer, and/or a company that makes living roofs. Smaller areas can most likely be tackled on your own.  You'll need to keep in mind the structural frame of your roof before deciding on the type of green roof for you. You don't want a lot of heavy garden up there if your roof won't support it! 

With that in mind, you should know that there are basically two types of green roofs:

1.  A shallowly planted roof (for smaller areas) 
2. A more deeply planted roof (for larger areas)

Shallowly planted roofs can be planted with lichens, mosses, small alpines, grasses. For deeper planting areas, you might consider wildflowers and some shallow rooted vegetables (or potted, like those fab garbage can potatoes!!) Biodiversity is the idea, to provide more available habitat for the fauna.

Plant in early spring or early fall or you may find that hot weather may defeat your efforts. Use high quality 100% organic compost to provide a perfect blend of nutrients to your plants. Choose the right mix of plants (with suggestions from your friendly neighborhood nursery or college horticulture organization) and your garden will be low maintenance, requiring just a little weeding and deadheading to keep your garden looking great!