Philosophy of Pruning Shrubs
For many flowering shrubs, yearly pruning is essential to encourage the regular development of flowers. There are some that need only the occasional cutting-out of dead, aged and crossing stems, but for others the removal of flowered stems encourages the further development of flowering shoots. A few shrubs need just the removal of dead flowerheads. If pruning is neglected, a shrub’s ability to produce attractive flowers is diminished.
Pruning Evergreen Shrubs
These are clothed in leaves throughout the year, with new ones being formed and old ones falling off. Do not prune evergreens in winter; mid- or late spring is the best time, just when growth is beginning. However, if the plant is flowering, defer pruning until the blooms fade. The usual reasons for pruning evergreen shrubs are to create shapely plants and to prevent them crowding out their neighbors.
Examples of evergreen shrubs include Berberis darwinii, Viburnum tinus, Hollies, Olearia x haastii, Choisya ternata, Phillyreas and most Escallonias.
Early-flowering deciduous shrubs – flowering from spring to mid-summer – are pruned as soon as their flowers fade. This gives a shrub a long period during the rest of summer and into early autumn in which to produce fresh shoots that will ripen and be frost-hardy by winter. From spring to mid- summer of the following year these shrubs bear flowers on new stems.
Examples of early-flowering deciduous shrubs include Deutzias, Philadelphus, Ribes (Flowering Currants), Weigelas and Syringa (Lilacs).
Evergreens For Flower Arrangements
Many evergreen shrubs are in demand by flower arrangers, especially during winter when there is a shortage of other plants. When cutting foliage, always take shoots from the back of the plant and select them from several different positions. Use pruning shears to cut stems just above a leaf-joint.
Late Summer-Flowering Shrubs
Late summer-flowering deciduous shrubs are pruned during the following late spring. This encourages the development of shoots that will bear flowers later in the same year. If these shrubs were pruned as soon as their flowers faded in late summer or early autumn, any shoots that developed from the cuts could be damaged or killed by cold winter weather. Examples of late summer-flowering deciduous shrubs include the popular Buddleja davidii (still often known as Buddleia davidii; Butterfly Bush), Ceanothus ‘Gloire de Versailles’ and Tamarix pentandra (Tamarisk). Incidentally, do not confuse this Tamarisk with the related Tamarix tetrandra, which flowers in spring and should be pruned as soon as the flowers have faded.
Winter-flowering deciduous shrubs need little pruning. When young, prune them to shape to create an attractive outline. Later in their lives – as soon as their display is over, usually by early spring – cut out congested stems and those that have become diseased or damaged by severe weather. If left, they encourage decay to infect and damage other parts of the shrub. Keep the shrub’s center open so that light and air can enter. Incidentally, it is easier to control the size of winter-flowering shrubs than any other type.
Examples of winter-flowering deciduous shrubs include Hamamelis mollis, Cornus mas and Viburnum x bodnantense.
Pruning A Dogwood
Several Dogwoods are grown for their colored stems, which are especially welcome in winter when they are free from leaves and low light can glance off them. Unless these plants are radically pruned in spring by cutting them right down to within 3 in (7.5 cm) of the ground, they will not produce their annual display. Shrubs to look for with attractive colored stems include Cornus alba ‘Elegantissima’ (red stems), C. alba ‘Sibirica’ (bright crimson stems), C. alba ‘Kesselringii’ (purplish-black stems) and Cornus sericea ‘Flaviramea’ (bright greenish- yellow stems); also known as Cornus stolonifera ‘Flaviramea.’
Dealing with Reversion
Occasionally, some variegated plants have stems that revert to an all-green nature. Usually, these are more vigorous than the variegated form and both look different from the rest of the shrub and stand above the normal level of the foliage. As soon as they are seen, cut back these stems to the variegated leaves.
More from Pruning:
Reprinted with permission from Pruning by David Squire and published by Fox Chapel Publishing, 2016.
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