Val Bourne on the best examples of mauve-lavender flowering plant

If you drive through the village of Bloxham in May, you can’t fail to notice the huge wisteria that festoons one house close to the village hall. I see it most years and this year it’s even more glorious than usual with racemes of mauve-lavender flowers supported by glossy young foliage that’s almost russet in colour.

It seems that the recent weather has suited wisterias down to the ground. They loved the Jubilee-barge summer of non-stop rain in 2012, the sunny summer of 2013 and the recent warm, very damp winter we’ve just had.

Wisterias are named after Caspar Wistar (1761-1818), a professor of anatomy at the University of Pennsyl-vania. It’s an early botanical typo that should really be Wistaria, but we stick to Wisteria. It’s a legume, as you can see from the pea-like flowers and, like all legumes, it shouldn’t be given extra nitrogen. Legumes fix their own nitrogen at the root and, if given extra, your wisteria will produce leaves at the expense of flower.

There are ten species found China, Japan and the Eastern USA. In the wild they are often found close to streams, near wet woodlands and close to damp cliffs. In our country they need warmth to flower abundantly and a west-facing wall is often cited as the best, although many inhabit more-southerly walls in London. The one direction to avoid is east-facing because, if your wisteria is beginning to leaf and bud up, a late frost followed by early morning sun can rupture the cells. Camellias and magnolias can also suffer the same fate.

Ten years ago a magnificent, elderly specimen of wisteria, growing on the tithe barn at Sudeley Castle, near Winchcombe in Gloucestershire, was killed by a late-May frost. Normally, though, wisterias live a long time. There is an ancient specimen straddling the old White Lion pub in Banbury, curling round a black circular staircase and some say it’s hundreds of years old. The way they climb has made them a garden favourite for walls, pergolas and arches.

However, in order to flower well wisterias need a two-stage pruning regime. By early July wisterias will have produced long shoots that are about a foot long. These need cutting back to four to six leaves, towards the ripened wood. Try to keep the shoots this length until the autumn if possible. Once the plant is dormant, prune again in Febru-ary or early March, leaving just two buds on each shoot to create a skeletal framework. This twice-yearly pruning regime lets in more light and ripens the wood, encouraging more flowering spurs and fatter flower buds. After a sunny summer your wisteria should drip with bloom every spring.

This twice-yearly prune also keeps the plant compact making it less prone to wind damage should gales occur.

Chinese wisterias (labelled W. sinensis) and Japanese (W. floribunda) twine in different directions and this confused me for many years. A simple way of remembering is to form the letter C with your finger staring at the top. This clockwise movement describes the way Chinese wisterias (W. sinensis) twine. Now make a J starting from the top and your finger will move in an clockwise direction — the same way the Japanese wisterias (W. floribunda) twine. Another way of telling is that W. sinensis produces its flowers on bare wood, whilst W. floribunda has leaves and flowers at the same time.