Pruning wisteria: when & how to cut back
Pruning wisteria is key to maximising their flowering potential. Read on to discover when and how to prune wisteria for the best blooms come summer.
Wisterias look magnificent when they flower from late spring to early summer. However, as vigorous climbers, they can put on a huge amount of growth each season. Keep reading to find out how to prune your wisteria to encourage more blooms and when the best time to prune is.
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Pruning wisteria: when to prune
If you are wondering when to prune wisteria, the answer is twice a year, in late winter and mid-summer. Here in the UK, pruning wisteria is usually a task performed in February and then again in late July or August. This bi-annual pruning not only helps keep these often-unruly climbers under control, but also encourages bud formation on the old wood.
How to prune wisteria
Whether you are lightly pruning wisteria as part of its bi-annual maintenance regime or cutting back harder, the correct tools and protective gear are essential. Ensure any secateurs, loppers or hand saws you plan on using are sharp and clean to help keep wounds to a minimum and prevent the transfer of any diseases. Remember that wisteria is poisonous, so gloves should be worn when handling any part of these plants. When pruning wisterias from a height, safety is also of paramount importance. Make sure you install a secure base from which to work.
Hard pruning
When training a wisteria against a wall as an espalier, pruning can help establish a good framework of branches. After planting a wisteria, prune the leading shoot back to 75 to 100cm above the soil, making a cut just above a bud, and remove any existing side shoots. As the leader and laterals develop over the summer, tie them where you would like them to grow. You can also reduce any new laterals back to three to four buds, which will encourage spur formation. In the second year, reduce the leader again so that it is around 75 to 100cm above the top of the side shoots. To promote strong branching, you can also prune the top third off any laterals and keep tying them in where you want them to grow.
Since wisterias are long-lived, there may be times when you need to hard prune wisteria in order to access the wall or support it is growing upon. You can also hard prune wisteria to remove old branches or those that are growing in the wrong place. Hard pruning wisteria is best done during the winter months when the leaves have fallen and the wisteria is dormant. Wisteria responds well to hard pruning and you can cut back to just above another branch or even back to the main trunk. Cutting wisteria back hard encourages vigorous new growth and also reduces the need for any fertiliser that year.
Summer pruning wisteria
After flowering, wisterias can put on excessive growth over the summer months when they are actively growing. To control the growth, prune the long new wispy shoots with secateurs back to around 30cm or 5 to 6 leaves in late July or August. Summer pruning wisteria will neaten its appearance for the autumn and help encourage flowering buds for the following year. You can also prune away any wisteria suckers that appear at the base of the plant and shorten branches that have outgrown their allotted space.
Pruning wisteria in winter or early spring
With the leaves having dropped over the winter, it can be easier to see the framework of branches when pruning your wisteria toward the end of the season. January or February is ideal for winter pruning wisteria as the new growth has yet to appear. To prune your wisteria in winter, shorten the shoots you previously pruned in the summer back to around 10cm or two to three buds from the branches. By shortening these shoots, the blooms will be more visible come early summer. With the leaves out of the way, winter is also a good time to retie any branches to their supports and remove any crossing, rubbing or dead branches.
Having cut back wisteria in the winter, you can further encourage your wisteria’s flowers by applying a fertiliser in early spring. A feed high in phosphorus, such as blood, fish and bone, is ideal as it will help encourage the round flower buds to develop into long racemes.
Bonsai pruning
Along with other species, wisteria is sometimes used for growing as a bonsai plant. However, only certain varieties are suitable and, as they are to be kept very small, more frequent and radical bonsai pruning is required.
Known for their purple-lilac blooms, white or pink flowering wisterias are another option for your garden. Learn more about the best wisteria varieties to grow in our separate article.
