Climbers: renovating overgrown plants
Climbers and wall shrubs can become overgrown, extending over the top of the fence or into nearby trees, often with reduced flowering. Many can be hard-pruned to renovate them, but some are best replaced.
Timing November-March for deciduous climbers; early spring for evergreens
Many wall shrubs that have outgrown their allotted space, or that have started to decline but are basically sound, can be renovated to rejuvenate them.
Sickly plants that are dying back and cannot be brought back to health are better removed and replaced.
Some climbers and wall shrubs do not respond well to hard pruning and are better replaced. Examples of these include Berberidopsis, Calceolaria, Carpenteria, Ceanothus, Clerodendrum, Clianthus, Coronilla, Cytisus, Dregea, Eccremocarpus, Fremontodendron, Hardenbergia, Hoya, Lapageria, Leptospermum, Metrosideros, Muehlenbeckia, Plumbago, Senecio, Solanum, Stauntonia, Strongylodon and Thunbergia.
If in doubt, look up individual plants in a pruning reference such as RHS Pruning and Training by Christopher Brickell and David Joyce, which is available to buy from the RHS Online Shop.
When to renovate overgrown climbers and wall shrubs
- Deciduous climbers and wall shrubs are usually renovated during the dormant season, between November and March
- Evergreen climbers are usually renovated in early spring
- Tender plants are best renovated in mid- to late spring, once the risk of frost has passed, to prevent the risk of cold damaging the new growth
Renovating overgrown climbers and wall shrubs
You can cut back climbers and wall shrubs quite drastically, and some will respond to this method. Others respond better to a gradually renovation.
Some climbers and wall shrubs tolerate drastic pruning and can be cut down to approximately 30cm (12in) from ground level. This drastic pruning means that flowering will take several years to resume, but allows new green shoots arising from the base to be trained into a new and rejuvenated framework.
Examples of plants that re-grow well from drastic pruning include: Abelia, Acacia, Ampelopsis, Aristolochia, Azara, Campsis, Celastrus, Cissus, Clematis, Cotoneaster, Hedera (ivy), Osmanthus, Pyracantha, Ribes sanguineum, Rosa, Vitis and Wisteria.
Some plants, such as Chimonanthus, Jasminum, Lonicera (honeysuckle), Parthenocissus and Polygonum (Russian vine) do better when renovated slightly less hard, cutting back to 60cm (2ft) from the base.
Cutting back to a framework
Some climbers and wall shrubs respond better when cut back to a main framework of branches, rather than to near ground level. Cutting to a bud or branch helps ensure that re-growth will be successful.
Examples of plants that respond well to this method include Actinidia, Billardiera, Bougainvillea, Callistemon, Escallonia and Passiflora (passion flower).
Other plants are better renovated gradually, cutting them back over two or three years. Each year, cut back one in three of the main stems to ground level, reducing the rest to half their length.
Examples of plants that prefer gradual renovation include: Chaenomeles, Forsythia, Garrya, Hydrangea, Magnolia and Schizophragma.
Tools and techniques
Use loppers for thick and woody stems up to 3cm (1¼ in) wide. Use a pruning saw for thicker branches.
Before pruning, detach the climber or wall shrub from its supports and lay it flat on the ground (if the stems are flexible enough). This allows tangled shoots to be sorted out, especially important where a main framework of branches is to be preserved.
This is also a good opportunity to remove debris from behind the supports and carry out repairs and maintenance as necessary.
In the spring, apply a slow release fertiliser, such as controlled release granules or fish, blood and bone, at 120g per sq m (4oz per sq yd) to the soil at the base of the plant. Mulch the root area with bulky organic matter to conserve moisture in the soil below. Water well in dry spells.
In the first year after renovation, tie new growth into the framework as you would for a new plant. In the second year after renovation, thin this new growth out, selecting the best-placed and strongest branches and removing the others.
Some plants, such as Chimonanthus, can be slow to respond to renovation. Do not be surprised if your plants do not re-shoot immediately after drastic pruning. Shoots can develop at any time over the growing season, or even in the following year.
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