How to Build a Rooftop Garden
Living roofs are increasing in popularity for a number of reasons: they can be grown in even tiny gardens; they bring color to bare, unused outdoor surfaces; they insulate your roof; and they can provide extra wildlife habitats. This simple plan uses just three cultivars of sedum to create a rich tapestry of red and gold. Sedums are ideal roof plants because they are drought tolerant and will cover the surface by forming a thick mat of succulent foliage. You will need approximately 5x8 feet (1.5x2.5 m) of space to grow these plants. These grasses, which are best-suited strong garden rooftops, prefer free-draining soil or and full sun.
- 10 Coral Reef (Sedum tetractinum)
- 10 Angelina (Sedum rupestre)
- 10 Spirit (Sedum selskianum)
- marine-quality plywood
- plastic liner
- general compost
- purpose-made sedum roof mats (optional)
Planting and Aftercare
Cut a piece of marine-quality plywood to the size of the roof, and cover it with plastic liner. Nail this securely to the roof. Create a 2 inches (5 cm) deep wooden planting frame on top by fastening planks of wood to each edge of the roof to form a sturdy framework. Fill the frame with a mix of perlite, insulation, and general compost. Drill holes into the wooden frame's bottom edge to promote good drainage. Push insulation into these holes as a filter to prevent the compost from draining out too. Plant the sedums into the growing medium. Sedums don't like wet roots so in fall or winter, clear the leaves that will have fallen on the plants, and check that the drainage holes are still open. Alternatively, purpose-made sedum roof mats can be bought that can simply be rolled out and attached. If you are unsure whether your roof can take the weight of the sedum planting design, check with an engineer.