The next thing to take into account is how much maintenance you are willing to do and are capable of. One of the greatest things about green roofs and walls is you can put as much or as little work into maintaining them as you want. If you choose low maintenance, planting local flora and fauna is your best choice because it is already used to the local climate, amount of sunlight and precipitation. If you would like to have a roof or walls that you can maintain you can easily plant a vegetable, herb or flower garden.
There are two main types of green walls to choose from: vines or planted. Vines are the easiest to maintain considering you choose vines that are a good match for your area. By talking to local green specialists or your local nursery you can easily find out what vines are your best options. You will want to know if the plants you choose will need a trellis to cling to as they grow upward or if they attach themselves to the walls. Another thing to consider is perennial vining plants will take some time to mature and work their way up your walls. In the meantime you may want to consider annual vines that grow quickly but have to be replaced yearly until the perennials take hold.
If you choose a planted wall there are several ways to go about achieving it. One option is to build a framework of squares that can support a potted plant in each square. A structure like this will need to be anchored to the wall that it is covering. A similar structure is built much like a bookshelf with the “shelves" angled upward at a 45 degree angle, providing long shelves to use as flower boxes.
One more option for a green wall includes combining the vines and planted styles. With a structurally sound trellis one could easily space out the potted plants to allow room for the vines to grow up in between and around the pots.
Whether you choose a green roof and walls that are physically attached to your house or part of a structural casing you will gain the benefits of reduced energy costs, beautiful greenery surrounding your home as well as the satisfaction of knowing that you are doing something to help the environment around you.
Planting Green Roofs and Living Walls by Nigel Dunnett and Noel Kingsbury, Timber Press 2005.