Sedum spectabile -- part of the Crassulaceae plant family -- are durable and hardy succulents also known as everlasting, showy sedum, balloon plant or stonecrop. Sedum plants are ideal for incorporating into an environmentally friendly "green" roof. Green roofs provide excellent insulation, keeping cold out in winter and cooling the home during hot summer months. Sedums are drought-tolerant, heat- and disease-resistant and easy to grow. Start with a small project. Create a roof on a garden shed, deck or playhouse to practice your building technique and determine which varieties of sedum grow best in your location and light levels.
Select low-growing varieties of sedum. Stonecrop (Sedum album), goldmoss sedum (Sedum acre) and golden sedum (Sedum adolphii) are ideal choices for green-roof cultivation. Purchase plants or seeds from garden and home-supply stores or order them online from succulent-plant nurseries. Plants can be divided and several new starts grown from one parent plant.
Cover the roof area of your project with tar paper or waterproof sheeting. Cut it to fit with a utility knife. Secure it with a staple gun and staples or hammer and roofing nails.
Add a layer of cocoa fibre or coir fibre matting. Cut it to fit and secure it to the roof with strips of treated 1-by-2-inch lumber and roofing nails.
Sprinkle a thin layer of growing mixture on top of the matting. Use a purchased cactus potting soil or a mixture of equal parts sand, potting soil and crushed lava rock.
Water the planting mixture lightly. Allow it to settle into the fibre matting. Tuck a few living sedum starts into the matting, spaced about 1 foot apart.
Mix seeds from another sedum variety into a pound of garden lime. Place the mixture in a shaker and broadcast it over the matting. The lime will nourish the soil; in addition, the white of the lime will allow you to see that you have even seed coverage.
Water the soil with a fine mist from a garden hose. Keep it uniformly moist, but not soggy, until the seeds have germinated.
Fertilise lightly with a half-strength mixture of organic fertiliser in the spring. Remove heavy leaf or debris accumulation from the sedum plants in the fall, using a leaf blower.
Sedums are very hardy and require little care. Sedum roofs can be walked on without doing damage to the plants. If a piece of leaf is broken off, it quickly roots again. Precut and assembled "green" roofing kits can be purchased from home and garden centres or online from eco-friendly roofing vendors.