Wisteria is an aggressive, fast-growing member of the pea family. A deciduous woody vine, wisteria is popular for its large, hanging flower clusters that bloom in the spring. Wisteria can be trained to climb over a pergola and offers shade in the summer once the structure is covered. Wisteria is a plant that demands pruning, both to control its growth on the pergola and to keep it flowering. Prune the wisteria in midwinter while it is dormant and again in the summer, two months after it finishes blooming.
Begin trimming the wisteria that is growing up the support posts and work your way up. Use the ladder to reach the wisteria growing over the top of the pergola.
Cut the current season’s growth back to within six buds from the main stem, or trunk, of the wisteria plant during the summer. Make the cut 1/2 inch away from the fourth bud.
Shorten the shoots to 2 buds in the winter, leaving 1/2 inch of stem beyond the second bud.
Cut any shoots that are growing too far from the pergola or aren’t in keeping with the shape you want to achieve. Cut these back to the desired length, within 1/2 inch of a bud.