Pruning with a Purpose: Shaping Plants for Special Effects
Some shrubs are grown for their foliage or for their colorful stems, which are at their best after leaf fall. By pruning these plants hard early in the year, you can create magical effects in the dark, cold winter months.
It might look brutal at first, but many shrubs respond positively to hard pruning by rewarding you with a mass of fresh, new, colorful stems, or by developing leaves that are much bigger, are a better shape, or are more colorful than those produced by unpruned plants.
A number of shrubs will become quite large if left to their own devices, but by cutting them back hard annually in spring, or at least once every few years, you can contain their size and also encourage healthy, decorative leaves. Avoid pruning plants in the fall, because decay fungi might enter the pruning cuts and cause damage or even death.
Before you start, check that specific plants will respond well to hard pruning. Remember that although cutting back will improve foliage or stems, it might also mean a loss of flowers for that season. Not all plants will tolerate hard pruning, and some may not survive such treatment.
Coppicing and Pollarding
Shrubs grown for their winter stems tend to merge into the background for much of the year, only coming into their own in the fall after the leaves drop. If left, their stems appear dull and lose their vibrancy of color, but cutting them back annually, or at least every other year, will promote a flush of new colorful shoots.
Willows and dogwoods can be pruned using a technique known as coppicing, which encourages a mass of colorful winter stems. Begin training plants just after planting by pruning back all shoots hard, close to their base. The following spring and in subsequent years, prune the tree in the same way to produce a stumpy framework.
Pollarding is another method used for pruning dogwoods and willows to produce spectacular winter stems. Instead of being pruned back close to the ground, plants are pruned above a clear trunk. The branches are cut back to previous cuts on the top of the trunk to leave a lollipop shape. After cutting back plants hard, feed around the roots and mulch.
Pruning for Foliage
Some shrubs are pruned hard to produce winter stems, and others can be given similar treatment to encourage more eye-catching foliage. The Indian bean tree (Catalpa bignonioides), Judas tree (Cercis siliquastrum), foxglove tree (Paulownia tomentosa), and others respond by producing larger leaves than those on unpruned plants. Cider gum (Eucalyptus gunnii) has curved, oval leaves when mature. If cut back hard, it responds by producing attractive juvenile leaves.
The foliage of many deciduous variegated shrubs is far more vibrant if pruned annually. The usual techniques for these plants are pollarding and stooling, which should be carried out between late winter and early spring, before leaves appear. To stool plants, cut back stems to within 2–3in (5–7.5cm) of the ground. To grow as a pollard, cut back shoots to within 2–3 inches (5–7.5 cm) of the trunk. Apply a balanced granular fertilizer at 2 ounces per square yard (70 g per square meter) to assist new growth after pruning. Prune back hard in the spring for a more impressive display. Certain plants produce their most attractive foliage with juvenile leaves.
Plants that Respond Well to Special Pruning
- Acer negundo 'Winter Lightning'
- Catalpa bignonioides (Indian bean tree)
- Cercis siliquastrum (Judas tree)
- Cornus species (Dogwood)
- Cotinus species (Smoke bush)
- Davidia involucrata (Handkerchief tree)
- Eucalyptus gunnii (Cider gum)
- Rubus species (Ornamental bramble)
- Salix species (Willow)
- Sambucus nigra 'Aurea' (Elder)