A rooftop garden can be a good alternative if you live in an apartment building or just have no available garden space. Roof gardens also help keep the rooms below them cool in the summer and provide extra insulation in the winter. The main problem rooftop gardeners face is wind, but with some modifications to your garden space, you can keep this problem to a minimum. While it can be a challenge to move the materials for a large garden to the roof, the rewards may be worth the effort.
Have a structural engineer inspect your roof to make sure it's waterproof and will be structurally able to hold the extra weight of planters, wet soil and people.
Check your local building codes to determine whether you need to obtain permits to build a garden on the roof or if safety railings or other structures will be required.
Make sure you will have a water source, electrical outlet and storage space on the roof.
Build fences or other barriers to act as windbreaks to prevent damage to your plants and keep the wind from drying your potting soil too quickly.
Build lattice trellises and grow vines on them, or build other structures to provide shade.
Locate the load-bearing joists and place your heaviest containers over them.
Choose the containers you will use for your rooftop garden. Terra cotta containers dry out quickly and may not be suitable for the windy rooftop environment; plastic containers are lightweight and better able to retain moisture. Whichever containers you choose need to have good drainage.
Use a lightweight, soilless potting mix for your rooftop garden.
Use hardy plants that are well adapted to hot, dry and windy environments.
Choose perennials that are hardier than your zone according to the USDA Plant Hardiness Zone Map. If you live in zone 7, for instance, use plants that can tolerate zone 5 or 6.
Pay careful attention to water. Plants grown in the hot, dry conditions on the roof may need to be watered up to two or three times each day.
Mulch around your plants to help retain moisture, or mix moisture-retaining crystals into the potting mix.
Use large, deep containers lined on the sides and bottom with a 1- or 2-inch layer of foam insulation to help protect permanent plants like shrubs, perennials and vines from freezing.
Apply water-soluble fertilizer regularly, or place slow-release fertilizer pellets in the top of the soil to provide nutrients for your plants.