Why won't a wisteria bloom? There are lots of possible reasons. Bad attitude, for one. This is a vine that wants its way in the garden. Show it who's boss—and persuade it to flower—with proper pruning.
Follow these step-by-step instructions to prune wisteria to make it bloom:
Roll Out a Welcome Mat
Above: Wisteria 'Blue Rain' blooms on a balcony railing in Antwerp. For more of this garden, see Radical Urban Gardens from Antwerp.
First things first. Despite its reputation as an invasive bully in the garden, wisteria can be finicky when it comes to performing. Buy a named variety from the nursery (rather than generic rootstock). The two most common types of Wisteria—sinensis (Chinese) and frutescens (native to American)—have varieties with blue, white, or purple flowers.
Plant wisteria in a protected, warm spot in full sunlight (try to get this right the first time, because it does not like to be transplanted).
Persistence Pays Off
Above: Photograph via The Martha Blog.
Martha Stewart has trained her wisteria plants to grow into small trees on her farm in Westchester County, NY. Whether you want a tree or a vine, you should prune wisteria each year to encourage it to bloom. And be patient: it can take two or three years of pruning to prompt it to bloom.
Survival Instincts
Above: Photograph by Bart Kiggen.
The next step is to understand wisteria's mentality. "Wisteria evolved where success lay in grappling up through a shaded canopy, putting lots of energy into climbing but none into blooming until it reached full sun and 'knew' it was at the top. There, both physical and chemical cues tell the vine 'this is it,'" says wisteria expert Janet Macunovich of Garden A to Z.
Wisteria wants to bloom when it feels increased warmth from direct sunlight and there is nothing above to climb.
"Choose a point that is 'top', train the vine to lay horizontally there and repeatedly clip off side branches that try to continue up," says Macunovich. "This allows the top growth to develop in horizontal position and without shading foliage above."
Mark Your Calendar
Above: Properly pruned, Martha Stewart's wisteria tree prepares to bloom.
Prune wisteria twice a season: in early March before it blooms and again in late summer to remove what Macunovich refers to as "whippy new growth."
Early spring before leaves appear is the time to hard-prune wisteria. On a new plant, choose a sturdy vertical-growing vine to be the leader and remove other vertical vines. You can train the leader against a trellis if you are growing a vine or stake it if you are growing a tree.
On the leader, encourage horizontal branching. Remove suckers (new growth that appears in the crotch of two branches.
The Mechanics
Above: Thin, immature tendrils (L) will not bloom and should be pruned or else the plant may put all its energy into producing leaves instead of flowers. Sturdy branches with buds (R) should be left on the plant until after its flowering season ends. Then you may remove as necessary to shape the plant. Photograph via Garden A to Z.
Diagram It: Wisteria Vine
Above: Encourage side branches spaced every 18 inches or so to grow horizontally from the leader. Image via Ohio State University. Hard-prune the vine in early spring and then cut off the season's tangly new growth in late summer.
Diagram It: Wisteria Tree
Above: Image via White Flower Farm.
To shape a wisteria standard, prune away long, thin branches that appear in summer. In late summer, plant specialist White Flower Farm advises, "cut the current season's growth back to just five to six large buds (leaving stubs about 6 inches long) and remove poorly placed branches entirely. This severe haircut controls growth and encourages some of the leaf buds to change into flower buds."
Tool Bag
Above: Loppers, shears, and hand pruners all are useful tools when pruning wisteria. Wear garden gloves to avoid scratches.
For more on wisteria, see:
- Wisteria: A Dangerous Beauty (Are You Tempted?)
- Paris in London: Neisha Crosland's Planting Scheme.
- DIY: Train a Wisteria Vine Not to Eat the House.
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