Compact or slender plants are perfect for balconies since they leave you with plenty of elbow room, while those who garden up on a rooftop should choose tough plants that can cope with strong winds and sun. Despite the limitations, there are plenty of options for these difficult spaces.
Most balconies are tiny, with just a few square feet for plants and people. To make the most of your available space, affix window boxes securely to railings and consider installing shelving units made from treated wood or metal. Decorate your shelves with herbs, alpines, and a few houseplants in the summer.
For year-round color, use slender conifers as well as box pyramids, spirals and other topiary forms to add lush tones. Also include a few fruits, such as strawberries and tomatoes, which will ripen quickly in a sunny spot.
Choose lightweight synthetic or metal containers for roof terraces where the total load-bearing weight is an issue, and make the most of any wall space by affixing pots or troughs to vertical surfaces to produce a layered effect. High winds can cause problems, so install windbreaks to make your space more usable. Line the boundaries with tough plants, such as Eleagnus x ebbingei, the bamboo Phyllostachys, Viburnum tinus, and Prunus laurocerasus to create a green shelter, or use wood, woven bamboo, or metal screens, but ensure that they allow 40 to 50 percent of the wind to pass through them to prevent turbulence.
With more shelter, your planting options expand, and you can include a range of flowering annuals and perennials, as well as edibles. Before buying plants, measure door widths and stairways to ensure you can move your plants up to the roof and you may need a crane for heavy containers and large trees.