It is important to know the weight your balcony will support, so check with the building engineer or building supervisor. Most balconies don't have built-in planters, so it is necessary to provide containers for the plants. Containers come in a variety of materials such as clay, plastic, wood and concrete. Clay is attractive and allows plant roots to breathe, but it can be heavy and plants require frequent watering. Plastic is lightweight, comes in colors, and does not require watering as frequently.
Wood also is fairly lightweight and attractive, but decomposes in time.
Concrete may match the material in the balcony, will provide good overwintering protection, but is very heavy. Small balcony spaces are more intimate than most other gardens. Keep in mind that each item will be viewed up close and must be chosen carefully. You don't want the garden and plants to over-burden the space. When selecting year-round plants for our balcony, needled evergreens are a good choice.