A Wisteria is a gorgeous plant when it is in bloom, a highlight of spring and a truly wonderful sight. But a lot of people buy one and within a few years become disillusioned and feel they have invited a monster into their garden, because this plant will soon cover an area a least 30 feet wide, or quickly climb to the top of a large tree. This can be fine if you have sufficient space, but few of us do. The answer is to prune it, but the pruning needed for a wisteria is different from that of most other plants. Unless you do it correctly, and at the right times, you might end up keeping your plant smaller, but the price will be few or even no blooms. A lot of the material on pruning wisteria is brief and inadequate, so let’s devote a whole blog to this, and turn something potentially tricky into something straightforward and fun. Once you learn how to tame it, a wisteria vine changes from a wolfhound into a poodle
Step One – Plan a Framework
The first thing to do, if you have limited space, is to decide on the final form of your plant. How much room do you have for it? Where to you want it to cover, and how far do you want it to go? Even with pruning these plants need a good amount of space, and 8 or 10 feet wide is about as small as you should consider, and 15 to 20 feet is more realistic.
You can grow a wisteria in several different ways, but they all involve some kind of permanent support system. These are strong plants, that develop thick trunks and limbs, so whatever support you use needs to be strong. A few bamboo canes are simply not going to do it. Think ‘four-by-four’ lumber, or solid steel rods that resist bending. If you have an existing pergola structure, or an open-frame gazebo, then that is an obvious place, if it is strong and well-built. You can also grow a wisteria against a sunny wall, but don’t bother with flimsy trellis panels, attach it to strong eye-bolts securely driven into the wall. You can also attach it to strong wires stretched across the wall, again secured to eye-bolts, with strainers to keep them tight, and spaced about 18 inches apart. Think about this – if you grow your plant on a high pergola, or up a high wall, you will need a ladder to prune it, so you need to be comfortable with that. Otherwise you should grow it on a lower structure, or as a tree.
Our top photo shows a wisteria trained into a tree, which is a wonderful feature, and often seen in Asian gardens. It is the perfect way to grow a wisteria if you don’t have walls or pergolas available – just make sure you have a four-by-four fixed firmly into the ground, and treated to prevent decay, as a permanent central support. You will probably need some additional horizontal supports for a few years at least, until the branches develop enough strength. We’ll come back to wisteria trees after talking about general pruning.
Step Two – Summer Pruning
A wisteria flowers first on the bare branches, before any leaves develop. Some varieties will also flower again, against a backdrop of green foliage.
After that first flowering on the older branches, long twining new shoots sprout out, and head in all directions, looking for support. With a new plant, use these – tying them in as they grow – to build the framework you want, which I why you need to think about that first. Once a new stem reaches the point you want it to stop at, cut the tip off. Once you have a rough framework growing, and in all the years that follow, keep trimming those green shoots several times a year. There doesn’t need to be much planning or skill here – just keep it tidy and cut back shoots that are getting out of hand. Keep it within the area you have given it, and be ruthless – you won’t kill it, and in fact the trimming stimulates the formation of flower buds.
Step Three – Winter/Spring Pruning
The main pruning takes place before the buds open, which can be early in some areas, so as soon as you see an increase in the size of the dormant buds, go ahead and prune. With no leaves it is much easier to see the framework you are making. You should be able to see, around the base of the shoots from last year, larger buds. These are the flower buds, and obviously you need these. The first step is to remove any dead branches, and on an older plant, any branches that have become too crowded. Cut these back right to the main branches.
The next step is to shorten back branches that grew last year. If you need them for the framework, then only cut them back as needed, if they aren’t for your framework, cut them back to just above the clusters of flower buds, only removing the part with the small leaf buds on it. Once you see the difference in bud-size this is easy to do. Usually this pruning will leave just a few inches of new stem. Now sit back and what for that glorious blooming, which will get better and better every year, soon giving you a controlled plant totally buried under blooms.
Creating a Wisteria Tree
Some additional pruning is needed to create a free-standing wisteria tree, like the one at the top. Use a strong support to hold up the trunk, which can be a single stem, or a cluster of a few stems, which is often how a plant looks when you receive it. They will grow together to make a picturesque trunk. Attach some horizontal bars to the main stake to support the crown while it matures. The pruning is the same as for a plant on a support, just more severe and organized. There is one extra thing, you must remove immediately any shoots you see growing from the trunk below where you have established the branches of the crown. A tree form like this can be trained as a neat dome, or developed with a more exotic or artistic look, depending on your garden style.
Love Your Wisteria
Now you have it under control you will have a gorgeous feature everyone will admire. Just a few hours of the year is all it takes, but the result is infinitely rewarding.
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