Summer prune wisteria

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Everyone dreams of having a well-groomed wisteria draped around the front of their house, yet its bi-annual pruning regime can seem daunting. If you prune it right – shortening the whippy tendrils at the end of summer then cutting them back again in winter – you’ll be rewarded with a neat framework bearing cascades of dangling purple, pink or white flower panicles in spring.

With an established plant like the one shown here, pruning seeks to restrain spread and create more flowering spurs.

“Vigorous whippy growth soon becomes a tangled mess,” says National Trust gardener Rachel Brown, who
works at Anglesey Abbey in Cambridgeshire. “The new growth will creep into gutters and twine around telephone cables. These growths need to be cut back in summer to form the spurs on which the following year’s flowers will grow. By cutting them back in summer, you increase air flow and allow more sunlight to reach the remaining stems, encouraging flower buds to form. The more you cut them back, the more congested the spurs, creating an attractive cascade of flowers next summer.

“The technique for pruning wisteria in summer is to cut back the new, whippy green stems to just four to six leaves; that’s about 15cm (6in) from the main framework. Cut just above the sixth leaf to remove the long green growth.

“It’s important to be able to tell the difference between this year’s growth (green) and last year’s growth (brown). The older brown stems form your permanent framework, which needs to remain intact – tied securely into trellis or wires using twine or soft ties looped into a figure of eight. “When you’re pruning in summer you can also remove any dead, diseased or damaged stems at the same time. Any basal stems and unwanted sideshoots can be removed too.

“In winter, you can cut back any subsequent long whippy stems that grew after the summer prune. Once the leaves are off and the plant is dormant, it’s easier to see the difference between the plump flower buds and flatter vegetative growth buds, so you’ll get a clearer idea of how many flowers to expect next year. Make the cut just above the third bud, about 2.5-5cm (1-2in) from older wood.”

How to shorten wisteria tendrils:

1 READ THE PLANT Understand the roles played by each part of your plant: the permanent woody framework (main stem and laterals) and whippy green sideshoots. It’s the latter that can be pruned to encourage new flower buds.

2 CUT BACK TO SIX LEAVES In summer, after flowering, cut back the whippy green stems (current year’s growth) to five or six compound leaves. These can be shortened again to two or three buds in winter, ensuring the spring flowers won’t be obscured by leaves.

3 KNOW WHEN TO STOP Leave intact these short woody spurs when shortening the whippy growth. This is where new flower buds will form; prune too hard and you’ll remove the potential for new flower buds. Also consider the plant’s overall silhouette.

FACTFILE:
Plant name:
Wisteria sinensis
Plant type: Deciduous climber
Why prune? To create a strong framework for the pendant summer flowers; allowing light to reach young shoots, encouraging them to ripen and produce new flower buds
When to prune? Midsummer after flowering (July-Aug) and late winter (Jan-Feb)
Other plants that can be pruned like this: Wisteria sinensis cvs; Wisteria floribunda and cvs; Wisteria formosa
Tools to use: hand pruners, loppers, pruning knife