If you live in the city and are fortunate enough to have access to a balcony or a flat portion of roof, you have the potential to create a thing of rare beauty – a “garden in the sky”. These areas present a unique challenge to the landscape designer, because they are liable to be in the path of every wind that blows, and scorched by sun. However, with careful planning and planting you can create a screen to block much of the wind, and some shade, either manmade (screens, awnings, canopies) or natural, to give protection from the worst of the sun.
The first essential in planning such a garden is to research the construction of the building. Find out what the roofing material comprises, or, if a balcony, how it is constructed. A balcony can be quite a small area – if it is to be loaded with containers (which, with their contents, can be very heavy) it must be able to support the weight. If you are building a garden on a roof, the roof must be made of waterproof material so that leaks do not occur, and there must be a good drainage system to carry away excess water. There also needs to be safe access to the roof from the floor beneath, if it is to be enjoyed readily.
Around your roof garden there will likely be poles or wires. These can be camoflaged with careful planting. Tall plants in containers can also screen you from your neighbor’s view and form a green haven, while smaller pots full of colorful flowers (for example, petunias and zinnias, in summer) will add some visual excitement. Be careful, however, not to overcrowd the precious space that you have available. Make sure there is room for somewhere to sit – and a pleasant view deserves to be framed rather than annihilated by a rooftop jungle.
Long wooden planters will spread the load and are preferable to using many small round pots. Remember to use a soil-moistening product in the container mix, which will help with maintenance, as plants in a mix containing these products require less watering. It may also be worthwhile to consider a hydroponics system, especially if the roof is structurally unable to bear much weight, since plants grown hydroponically require only a liquid medium, which weighs less than containers full of soil.
Your roof or balcony garden is also a good place to keep a small wormery or a bokashi system, so your precious plants can benefit while you are disposing of household waste in a way that is both useful and ecologically sound.