Different pruning techniques are used on shrubs, depending on the desired effect. Formal hedges, topiaries, and other closely clipped forms are sheared, which means all branches are clipped to the same length for a smooth edge. Some shrubs that bloom on new wood are also sheared back annually to the base to encourage a maximum number of branches and, thus, more flowers.
When a more natural shape is desired, shrubs are generally thinned, especially fast-growing types of deciduous shrubs such as forsythia and weigela. Older or excessively long branches and weaker secondary branches are removed down to a main branch or to the base of the plant. This allows room for younger branches to grow, producing a heavy flush of flower buds for the next bloom season. Thinning (renewal pruning) is usually the preferred method for pruning spring-flowering shrubs and is carried out as soon as the year's flowers have faded. The prunings can sometimes be used for cuttings.
When pruning, begin by removing old, weak, damaged, or crowded branches at their base. But don't indiscriminately shear off the top of the plant. The terminal buds on the branch tips release hormones that encourage root growth and maintain a slow, orderly pattern of growth. These are both desirable qualities worth preserving in your shrubs.
Consider changing an overgrown shrub into a multistemmed tree. This works nicely with flowering plums, black haw viburnums, winged euonymus, and lilacs, all of which can grow to be 12 to 15 feet tall. Begin by removing small, crowded upright stems to reveal a handful of shapely mature branches that can serve as trunks. Cut side shoots off the trunks up to about five feet off the ground, creating a tree form. Continue pruning as needed to keep the trunks clear of growth.
In general, vines should be treated in the same manner as shrubs. Vines grown for their foliage often produce overly exuberant growth, especially once they are established. They need to be pruned regularly and can be pruned at any time except late summer or early fall. Pruning at that time of year can result in new growth that does not have time to harden properly before winter arrives.
Keep reading to learn about trimming and deadheading.