How to prune wisteria
Climbing plants, including wisteria and clematis, bring height to the garden and add interest to buildings and garden structures. John Hoyland offers advice on how to prune wisteria effectively to ensure abundant flowers and foliage. Photographs Gavin Kingcome
Any nurseryman will confirm that one of the most common problems gardeners ask them about is the less-than-exuberant performance of climbing plants: wisteria with plenty of growth and no flowers; clematis with a topping of flowers and bare stems; honeysuckle and jasmine that grow into dense thickets of woody stems. The solution to all these problems lies in both pruning the plant correctly and in training it against its support in a way that encourages flowers rather than foliage. To get most climbers to flower well it is essential to begin forming the basic shape you want the plant to grow into as soon as it is planted.
Head to our piece on making your own plant supports for plants including climbers.
How to prune wisteria
Wisteria is a vigorous plant that will produce lots of long, whippy shoots, which, if left uncontrolled, can dislodge roof tiles, clog gutters and creep into attics. Even worse, they won’t produce any flowers. For best results, in August, tie in any stems that are needed to fill in gaps against the wall, or to extend the plant over a pergola. Cut back all the rest to about 30cm from the point from which they have grown. Some gardeners leave this job until the following spring, but doing it now not only makes wisteria look neater, it also lets the sun into the plant to ripen the young stems. This is important for future flower-bud production.
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The following February, shorten the stems that you pruned in the summer to about 5cm from the old wood. Doing this will create short, stumpy shoots known as spurs. If you look closely at these spurs there are usually two sizes of bud: short, thin ones and fat, plump ones. The plump ones are the flower buds; the thin ones will produce more shoots. More long shoots will have grown since the summer. Prune these back to four or five buds from the main stem, making the cut just after a bud.
February is also the best time to tackle wisteria branches that are growing away from the wall, or to remove old, woody branches from mature plants. Saw these off just above a young, vigorous branch or shoot. If the branch is very long, remove it in sections.
When to prune wisteria
Tie in wisteria stems that are needed to fill in gaps, then cut back stems severely to 30cm from their growing points.
Shorten previously cut stems to 5cm from the old wood. Prune back any new long shoots that are growing away from the supporting structure, cutting stems just after a bud.
If you follow a strict pruning regime for your wisteria, you will be rewarded with showy pendant racemes of fragrant flowers.
How to prune clematis
In an attempt to simplify the pruning of clematis, nurseries classify them into three groups with distinct pruning requirements. This grouping is based on the parentage of the plant and when it flowers. If you don’t know what group a clematis belongs to, prune it in relation to when it flowers.
Very early, spring-flowering and evergreen clematis only need pruning to remove damaged stems and reduce their size. Forms that produce large flowers in May and June should have their stems cut back to a pair of fat buds in February. Clematis that flower from late June and July should be cut back hard. Remove all growth to a pair of buds about 30cm from the ground in February or early March. The first time you do this can be unsettling – especially when you can see new growth appearing further up the stems you are cutting off. But hold your nerve, cut the whole plant down and a few months later you will have lots of young, fresh vigorous growth covered in buds and flowers.
Using ladders to prune wisteria and other tall climbers
- To prune tall climbers you will probably need to use one of the most dangerous tools in the garden: a ladder. It sounds improbable, but ladders are one of the biggest causes of accidents in the garden and every year about a dozen people die from falls off ladders.
- If you are using a ladder against the wall of a house it is worth taking the time to tie it in and to have someone at the foot of the ladder to steady it.
- Stepladders should always be placed on solid ground, never directly on to the soil. Falling even a few feet off a stepladder can be very painful.
Here's our round up of the best ladders for garden jobs.
Pruning passion flower
The passion flower, Passiflora caerulea, and both winter-flowering and summer-flowering jasmines, are spirited plants that need attention to prevent them becoming rampant. In early spring, cut old, flowered stems of passion flowers to the ground (or main trunk if you growing it over a pergola). Cut lateral shoots to about 15cm long. Immediately after flowering, cut the stems that have had flowers on back to the base. This can seem drastic, and it is tempting to simply shorten the stems to form an attractive shape to the plant, but this will lead to a dense, congested shrub.
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