Because you often want plants to be decorative or trained to fit a particular size or shape, training and pruning plays an important part in the balcony garden. Pinching out the tops of plants will encourage good bushy growth and prevent them getting leggy. Some plants, such as heather and shrubby herbs, can be lightly clipped after flowering to keep their desired shape. Only shrubs, trees and climbers will require any kind of formal pruning and even that should be just enough to maintain a good shape or to encourage flowering. Hard pruning produces vigorous growth, while a lighter pruning encourages more flowers and fruit.
Pruning shrubs
Flowering shrubs should be cut back in spring or late summer after they have bloomed. This is a good opportunity to get rid of any dead or diseased material and will encourage strong shoots next season. Cutting back the stems of a pot-grown rose by about half after the first frost will prevent wind damage in winter.
Pruning climbers
Light climbers like ivies need only trimming into shape. Vigorous flowering climbers, such as jasmine and honeysuckle, do not normally require pruning unless you want to reduce a tangled mass, but it is a good idea to remove any dead or diseased stems to keep the plant in good health. Evergreen climbers are generally pruned in early spring and deciduous types in winter. Wisteria is normally pruned in mid-summer, cutting the side shoots back to about 15 cm (6 in), and again in mid-winter when they are shortened to two buds. Cut back the side shoots of climbing roses to within one or three buds of the main stem; rambling roses can be completely cut back after flowering. Clematis plants are pruned according to their group, so check that with your supplier before proceeding.
Pruning soft fruit bushes
If you want to try growing fruit on a small balcony, perhaps against a sunny wall or trellis, then pruning a soft fruit bush into a pot-grown bush, or growing one of the two-dimensional trained effects, is probably the only way you will find the space. With soft fruit, the new side shoots are pruned back to the main stem until the desired shape is reached. Many trees and soft fruits can be grown in fan shapes to enable the branches to receive the maximum amount of sunshine. There are also cordon and espalier forms, involving strict pruning and tying techniques, to create horizontal forms that encourage maximum fruiting in the minimum of space. A specialist book will advise on the best way to prune and train fruiting trees and shrubs.
Pruning to achieve an ornamental effect
Other ornamental features are possible if you have the patience; fast-growing evergreen trailers and climbers can be trained over wire shapes to produce a quick topiary effect. Alternatively, slow-growing, small-leaved evergreens, such as privet, yew and box, can be clipped into formal shapes if you have the patience. Clipping normally takes place at the end of summer.
Standards are also popular for balcony containers and many shrubby or semi-shrubby plants, such as roses, fuchsias, fruit trees and bay trees, can be trained into this classic tall-stemmed lollipop form. This involves removing all the side shoots from the main stem of a rooted cutting but leaving the foliage on top. When the plant reaches the required height, the top is removed and the side shoots are allowed to develop, with the growing tips pinched out to encourage bushy growth until the required shape is achieved.