Wisteria hysteria,
Treat it well and your wisteria will be a joyous showstopper
What could be prettier than a mature wisteria in full flower? Whatever the variety, those hanging racemes in blue, lavender, mauve or white are magnificent. You won’t see the flowers before april, but if you want to plant a wisteria, this is an excellent time. and if one already thrives in your garden, it will benefit from pruning in January.
Wisterias also have off-season value. the leaves can be bronze when newly emerged, goldengreen through summer, warming to yellow ochre in October. aged stems are wonderfully roped and contorted. Of the ten species, Chinese
Wisteria sinensis and Japanese W. floribunda are the most popular. the former blooms on naked stems with leaves following. With Japanese wisteria, flowers and leaves appear together a tad later.
the most dependable Chinese type is Prolific — with mauveblue flowers and bronzy young leaves. among Japanese wisterias, I love W. floribunda alba for its long, white racemes.
american native W. frutescens grows as a gangling, but pretty, shrub. the variety amethyst Falls slumps against an old brick wall in my garden, where it produces dumpy, purple-blue racemes in early summer.
PERFECTLY FORMED
YOu might consider wisterias too big for tiny gardens. But with pruning and training, you can keep them to any size. they’ll grow in containers, too.
I’ve trained several to develop as small trees. to do this, begin with a 1.5-2m nursery plant. Prepare a planting hole, drive a 1.8m vertical pole into it, then plant the wisteria.
untwist the stems from their cane and tie them gently to the pole. Remove sideshoots and buds along those stems and don’t let any more come.
Leave up to five evenly spaced shoots or buds near the top. these will become branches, which can be trained.
Your aim is for an umbrellashaped tree, and metal wisteria trainers, though expensive, are available ( harrodhorticultural.
com, from £265). I prefer to run a string from the end of each lateral branch to the pole, flexing it slightly downwards. In time, those upper laterals will produce their own sideshoots. to maximise flowering, shorten those each august.
BOOST FLOWERING
the most common wisteria problem is failure to flower — which is easily remedied, if you know what makes wisteria tick.
a wild seedling takes years to climb from forest floor to sunny treetop before blooming. But we want ours to do this pronto.
to achieve that, choose named varieties — they’ve been selected to flower young. they are always grafted. New shoots that grow below the graft, at the base, are suckers and must be removed.
always plant wisterias in sun. the roots are fine in shade, but stem buds must ripen in summer sun to develop flowers.
Increase blooms by training. tie in young stems as they grow to develop a fan shape or parallel horizontal lines. Curve them round pillars or arches. When stems are tied in flexed positions, flowering is stimulated.
Increase this by pruning. Mature plants produce many long stems each summer. Cut these back to 10-15cm lengths in august and shorten them further, to two buds, in January.
Follow those simple rules, and your wisteria should become the envy of the neighbourhood.