WISTERIA’ S PURPLE REIGN
Dry conditions last year gave a boost to this British favourite
We’re enjoying a bumper year for wisteria. Last summer’s drought will have stressed the plants, making them set more flowers than usual for this spring.
The name brings one plant to mind, a familiar climber with hanging stems of beautiful violet mauve flowers in spring.
But there are ten wisteria species and more than 70 garden varieties. The two most loved are Chinese Wisteria sinensis and Japanese W. floribunda. The former blossoms on naked stems with leaves emerging as the flowers fade. With W.
floribunda, flowers and foliage usually come out together.
The flower stems or ‘racemes’ resemble huge, tapering catkins. A single bloom has the classic ‘ pea- flower’ formation. Five petals include a broad ‘standard’ at the top, two ‘wings’ at the sides and a ‘keel’ at the base.
Chinese wisteria is loved because the flowers show so well on the naked stems. Japanese wisterias have longer racemes. Being later to bloom, they’re less susceptible to late frosts.
SUN LOVERS
To flower well, wisterias need sun and warmth. A south or south- west wall is best but they’ll thrive in almost any sunny spot.
Most wisterias can grow to become a sizeable tree. But by pruning and training, you can keep the same plants to any size — even a bonsai. With age, the trunks and main stems can twist like massive barley sugar sticks. Side- shoots become gnarled too, looking ruggedly attractive in midwinter.
You can train wisterias onto supports or even raise them as free-standing, umbrella-shaped trees. To do that, use a stout support post about two metres high. Young stems can be tied to the post.
As the plant matures, allow lateral shoots to grow, but only from the top of the plant. When these develop, save the best-positioned to create your tree canopy.
Training for walls or a pergola is simpler. To develop the plant’s structure, arrange the best young leads evenly, tying them into place. Position them horizontally or at angles but never vertically. remove surplus or unwanted growth in winter.
For improved flowering, prune in August. Cut away all newly grown, whippy stems, leaving stumps with up to seven buds or leaves to flower next spring.
SPECIAL VARIETIES
AMong varieties, Prolific is one of the finest Chinese wisterias. The plant flowers freely, even when young. Among crossbreeds, W. x valderi Burford has beautifully bronzed young leaves which set off the soft white and deep mauve sprays.
The racemes can be more than 30cm long and as they lengthen, the leaves turn from bronze to bright green. Autumn foliage is golden yellow and falls late. From America comes Wisteria
frutescens, a sprawling shrub rather than climber but growable against a wall. The most common variety, Amethyst Falls, has tightly bunched flowers in a violet mauve.
I grow W. floribunda Alba as an ‘umbrella’ tree. The extralong, white flowers hang below a green foliage brolly. It’s vigorous and needs strict pruning.
Spurred on by that success, I planted a Japanese Silky Wisteria, W. brachybotrys Iko
Yama Fuji, to make another free-standing tree. At this early stage it’s like a bent fishing rod rather than an umbrella. But the massive violet blossoms already look sensational.