The wisteria has overwhelmed many a hobby gardener with its irrepressible growth. To keep it in check, you'll need to prune it twice a year - but its gorgeous blooms are well worth the effort.
Wisteria, also called wisteria, needs to be pruned twice a year in order for it to flower reliably. This rigorous pruning of the flower-bearing short shoots of the Chinese wisteria and the Japanese wisteria takes place in two steps - once in summer and then again in winter. The wisteria is a twisting, up to eight meter high climbing shrub belonging to the family of the butterfly family. It has the pinnate leaves typical of this family and, depending on the species and variety, shows clusters of blue, pink or white flowers that can be up to 50 centimeters long. The flower buds develop on short shoots on mature, old wood. Wisteria propagated from seeds take at least seven to eight years to flower for the first time. Refined specimens or specimens drawn from cuttings usually come from flowering mother plants without a special variety name. They bloom earlier and usually much more abundantly than seedling plants.
When and how to cut wisteria
Wisteria is cut twice a year: in summer and in winter. In summer all side shoots are cut back to 30 to 50 centimeters. In winter, the short shoots that have already been cut back in summer are shortened to two to three buds. If the abundance of flowers diminishes over time, overaged heads are also removed.
Wisteria are frost hardy, but love warmth. They thank sunny locations in a protected location with rich flowers, nitrogen-containing soils, however, lead to increased vegetative growth, which is at the expense of flower formation. Sometimes they can compress gutters and rain pipes or bend railings with their looping, woody shoots. That is why the attractive wisteria require garden walls, fences, very stable pergolas or massive rose arches from which the flower clusters hang down picturesquely. Wisteria can also be raised on the wall as a trellis or as a high trunk.
In the case of established plants, the goal of maintenance pruning is to limit the spread of the plant and to encourage the formation of as many short flowering shoots as possible. To do this, all short shoots are shortened in two steps. In the summer, about two months after flowering, cut all side shoots back to 30 to 50 centimeters. If new shoots arise from this, break them out before they lignify. This slows down growth and stimulates the formation of flower buds.
The second cut is due in the following winter. Now shorten the short shoots that have already been cut back in summer to two or three buds. The flower buds are located at the base of the short shoots and can be easily distinguished from the leaf buds because they are now larger and thicker than them. Over the years, thickened "heads" develop on whose short shoots most of the flower buds are formed. If the abundance of flowers subsides, gradually cut out the oldest branches with the "heads" and pull in new short shoots willing to bloom.
Wisteria are very long-lived climbing shrubs. With regular pruning, a tapering cut is not necessary. If the climbing bush has become too big, this can be done gradually over several years. Always cut out one of the main shoots and integrate a suitable replacement shoot into the frame. In an emergency, you can cut the wisteria back to a height of one meter and completely rebuild the crown in the following years. However, this is only recommended if your wisteria has not been cut for a number of years.
In the case of refined wisteria, make sure that the underlay does not drift through. Consistently remove all shoots that emerge at ground level, as these are very likely to be wild shoots. The upbringing cut depends on whether the wisteria is to be drawn on a pergola or as a trellis on a wall. In all cases it is important to build up a framework from a few shoots, which is preserved for life and on which the short flower-bearing shoots form. It takes at least three to four years to build a suitable framework, regardless of the type of growth chosen. The flower buds for the following year always form in the course of summer at the base of the new shoots. If the wisteria is allowed to grow without training, then the shoots will tangle up in one another, making a cut impossible after just a few years.
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For training on a pergola or a rose arch, tie the two to three strongest main branches to the climbing aid. If the shoots wind around the scaffolding, then loosen them and tie them down as well. Shorten the extension shoot to about one meter each year in late summer or winter. The resulting sap accumulation stimulates the plant to form side shoots, which are cut twice a year, as described for the maintenance pruning.
If you want to raise your wisteria on a wall trellis, cut the young plant to about 70 to 90 centimeters above a strong eye. Remove any side shoots and attach the shortened leader shoot to a stake. In summer, leave only two side shoots and guide them up the trellis at an angle of 45 degrees.
Shorten their side shoots again to about 10 to 15 centimeters. In the winter of the second year, cut the leading shoot about 70 to 80 centimeters above the top branch, shorten the side shoots by a third and tie them down. In the summer of next year you shorten the leading shoot again and now guide the next pair of side branches upwards at an angle. Shorten all branches of the side branches again to 15 centimeters and remove the superfluous and unwanted shoots on the base and on the main shoot. Follow these pruning rules until the plant has enough pairs of side branches to fill in the trellis.