October 24, 2009
WHEN THE buckeyes and maples announce the change of season and begin to shed their multi-colored leaves, my garden thoughts revolve around pruning my trees, shrubs and perennials.
At the top of my list this year will be an 8-year-old wisteria, running wild along a trellis at the end of the garden.
I know wisteria can be tricky. If you do it wrong, you get lots of new foliage and few flowers. The point is to prune it enough to control and shape its growth, and to encourage its splendid spring flower display.
There are several good pruning books: "Pruning and Training" by Christopher Brickell, Sunset's "Pruning," and "The Pruning Book" by Lee Reich. To my aid came the latest issue of a small quarterly I enjoy: "The Journal of Japanese Gardening."Ê Let me share with you some of the practical advice from an article, "Wisteria Pruning."
It helps to understand wisteria's growth habits.
Shortly after flowering in the spring, wisteria sets new flowering and foliage buds, but it is difficult to distinguish between them. By winter, however, flowering buds will be fatter and more clearly differentiated from the smaller foliage-producing buds.
The key is to prune to preserve the flowering buds as much as possible while cutting back the foliage producing buds to control growth. So, in summer (yes, summer), remove spent flowers and lightly prune the whips at the tips. Cut back any vine-like stems that are encroaching too far from the home trellis, wall or fence. The idea is to discourage rampant growth, but not too much. Wisteria benefits from growth for photosynthetic gain, and too much pruning will produce massive sprouting and disrupt the plant's energy gain.
In winter, when it is obvious which of the buds are flower-producing, prune more severely, cutting back stems to within 6-8 inches of their base, leaving five to seven buds on each. This is a bit of work, especially if your trellis is high, as mine is, and you have to work from a ladder. It also feels slightly brutal, but persevere. You will end up with a cleaned-up woody structure, with stubby cut branches and short flower stems, not unlike irregular fingers, each with numerous flower buds on them.
If your wisteria is old and neglected, the pruning procedure is based on the same principles, but may take two or three years before you get the vine the way you want it. Remove only one or two main branches each year, but treat the stems much as I've described.
"The Journal of Japanese Gardening" article also encourages keeping the entire plant above the trellis or arbor, and preventing the flexible whips from wrapping around the trellis structure. This is to allow the trellis to be repaired or parts replaced easily. When pruning, keep in mind the entire plant (some are huge) and how to shape it to fit the space in your garden.
Wisteria is a versatile addition to most gardens, and is delightful when it bursts forth with its fabulous, fragrant flower show in the spring, April to June in West Marin.
Most often, it is grown on a trellis, along a fence or eve, or espaliered on a wall. Wisteria also can be trained as a standard and grown in pots, creating graceful, miniature flowering trees for a patio or terrace. As to care, wisteria prefers limited fertilizer and water, and will thrive in full or partial sun.