Roof gardens, also called green roofs, are an environmentally friendly of utilising empty space on traditional roof. Roof gardens are speciality gardens increasingly common around the world, according to the University of Arizona, and can be easily planted in many ways. Whether planting an extensive roof garden with a thick layer of soil, turf grass and a wide variety of plants; or simply growing a thin layer of drought-tolerant sedums, many types of plants are available.
Place several layers of material onto a roof before planting plants. A strong, waterproof layer protects the roof from standing water and damage from plant roots. Waterproof-layer materials are the most expensive component but are also the most important. A drainage layer of simple fabrics or drainage troughs prevents water from collecting in large pools. The final layer is of artificial soils composed of lightweight materials retaining moisture and providing nutrients.
Sedums are the standard plant for roof gardens, according to Temple University. Sedums are a highly drought-tolerant group of plants, often called stonecrops, with shallow root systems that survive the harsh growing conditions of rooftop environments. More than 300 species of sedums are native to the Northern Hemisphere and the plants come in a variety of shapes, sizes and colours. Many sedum species are showy and develop numerous small flowers during the growing season. Sedums are hardy plants growing in shallow soil. They require little care once established on roof gardens.
Native grasses with shallow root systems readily grow on roof gardens. Grasses provide height to the roof garden and are attractive, as they sway in the breeze. Grass species; such as cheatgrass, Canadian bluegrass, fescue and spike melic; are common for roof gardens. Native grasses are also a common choice. However, some native grasses may not grow as well as non-native species, according to the Chicago Department of Environment.
Native wildflowers provide colour and interest. Many wild flower species grow in full sunlight, are drought tolerant and self-seed, so they reappear year after year. Wildflowers also attract beneficial insects to roof gardens and increase biodiversity in the local environment. Wild flower seed mixes are available from most nurseries, and flowers grow in established roof gardens without additional care.
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- University of Arizona; Green Roofs are Growing; Jeff Schalau; Oct. 7, 2009
- Chicago Department of Environment: A Guide to Rooftop Gardening
- The Pomegranate Center; Green Roof Manual; Alyssa Martin; 2005
- Washington State University; Stonecrop; Cheryll Greenwood Kinsley
- Temple University: A Green Roof Garden Primer