When and how a shrub should be pruned is determined by the kind of wood on which the flower buds are formed. It is important to nkow this so that the best effects are obtained. Shrubs fall naturally into two groups:
- Those that form their flower buds on shoots arising from the previous year’s wood.
- Those that bloom on shoots made during the current season.
Pruning early flowering shrubs
Generally, those plants that bloom before the end of June produce their blooms on growth made in the previous year. This is the largest group of shrubs and includes varieties of such plants as Forsythia, Viburnum, Deutzia, Bridal Wreath Spiraea and Mock Orange. These plants should all be pruned shortly after flowering.
The pruning process involves removing some of the old wood (more than 2 years old) closely from the base of the plant. This thins the plant to allow more available light to the central shoot, and encourages the development of new branches for subsequent bloom production. it also keeps the shrub filled with young wood. early flowering shrubs can be sheared into formal shapes such as squares or globes with one or two shearings per year if desir. For this process hedge shears should be used.
Pruning late flowering shrubs
Summer and late blooming shrubs flower at the ends of branches grown during the current season. Examples of this group are Snowball Hydrangea, Spiraea Antony Waterer and Butterfly Bush. These shrubs are pruned early in the spring before growth starts. The pruning consists of removing last year’s growth back to two to four buds from the base. The new growth from thse buds will provide the shoots on which the flowers will be borne.
Pruning of tree types like Lilacs and Rose of Sharon need special care. First remove the dead flower heads to prevent seed formation. This retains the plant’s energy and maintains its vigor. Then lightly thin out the plant to permit air circulation and light penetration. When thinning, remove old, twisted interfering shoots first, then prune for shape.
Annual Thinning
A. Unpruned shrub shows old wood and a lot of intercrossing growth.
B. Pruning has removed about one-third of the old wood and the least desireable of the crossing branches. Most of the young flowering wood remains.
C. Shearing to a formal shape.
Grafted and budded shrubs like Flowering Almond, Rose Tree of China and Purple Sandcherry have a tendency to develop suckers which should be removed. Usually, suckers are more vigorous than the grafted plant and when they are allowed to grow unchecked, the desired variety is seriously weakened. Look for the origin of the suspected branch and if it comes from below the graft, remove it as closely as possible to the main root. To prevent the occurance of sucker growth, grafted plants should be planted with the graft union 3-5 cm (1-2″) below the soil level.
Courtesy White Rose Nursery
