https://www.hopesgrovenurseries.co.uk/wp-content/uploads/2024/02/bd1-750x563.jpg GROWING AND PRUNING WISTERIA

Although we’re used to seeing wisteria climbing walls, festooning bridges and spanning pergolas, their fragrant, late-spring flowers must have seemed incredibly exotic to those gardeners who’d previously had to make do with simply shaped roses and sweet woodbine instead. Their cascading pea-like flowers, which mostly arrive as spring begins to welcome summer, define them as members of the legume family. They’re known for fixing their own nitrogen, through their root nodules, so avoid using avoid nitrogen-rich fertilisers. It will make them too leafy. Give them a light, flower-inducing, potash-rich feeding regime instead. Once a year is enough, just as they begin to flower.

Find them a warm, sheltered wall that faces south or west. Of the two south is definitely best, because these majestic, long-lived twiners often enjoy a steamy rainy season followed by summer heat in their native lands. They do not flower prolifically on north-facing walls and east-facing positions expose the emerging foliage to late May frosts. And that can be fatal. I can recall a huge wisteria, some hundred or so years of age, being killed off on the ruins of Sudeley Castle’s Tythe Barn near Winchcombe after an exceptionally chilly May night. For this reason, frost pockets must also be avoided.  When planting, don’t tuck them up right by the wall either. It’s too dry. A metre away is perfect (for wisteria and any other wall shrub or climber). Once they head upwards and reach their desired height, you can tie them into supports closer to the wall.

All four wisteria species occur naturally in woodland or in woodland margins, but they twine towards the sun so they need a sunny location to flower well. There are four species of this deciduous, woody vine in all. One species is native to North America and the other three are Asian. Although these four species are separated into separate parts of the world now, before continental drift occurred these twiners would have been found in the same land mass. Asian hydrangeas, witch hazels, mahonias, acers and magnolias also have American cousins. They simply drifted apart. Parts of Asia escaped glaciation, so their flora tends to be richer.

They’re were named Wisteria by Thomas Nuttall, an English botanist, ornithologist and member of the Linnean Society, who travelled to North America in 1808. He wanted to honour Caspar Wistar (1761 -1818), an American physician and scientist. However, some of the wealthier members of Wistar’s family had already Anglicized their name to Wister from 1727 onwards. Confusion arose, or day I say ‘wisteria hysteria’, until Wisteria was finally accepted as correct.

The North American, late-summer flowering species, Wisteria frutescens, was the first to arrive in the UK under the name Glycine. Seeds were sent to the Chelsea Physic Garden by Mark Catesby in 1724, a pioneering English naturalist who travelled to the New World. Its common name, the Carolina kidney bean tree, is named for the slender, velvety pods that follow the flowers. In the wild it’s found on either side of the Appalachian Mountains in eastern USA.

Catesby also sent some of these bean-like seeds to a Kensington nurseryman, Robert Furber, who named it Catesby’s Climber. In those days Kensington was the epicentre for newly collected plants and leading nurseries. There are some very handsome wisterias planted on grand 18^th century town houses in the Kensington and Holland Park district of London. There’s also a Japanese Kyoto-style garden in Holland Park.

The other three species of wisteria are Asian.

Wisteria floribunda, found in southern Korea and Japan, bears shorter racemes and is commonly called Japanese wisteria. The fragrant flowers vary in colour from purple-blue through to pale-blue, pink and white. It’s worth noting, at this point, that paler-coloured flowers contain less pigment and more air in their petals. Paler flowers (of all types) tend to brown as they fade.

Japanese wisteria, which is found naturally in woods and forests above 1200m, has been grown in Japanese gardens for centuries and many cultivars have been named. Flowers generally appear from spring to early May. You can identify Japanese wisteria, because the greyish stems twine in a clockwise direction. A good way to remember this, as I was told as a child, is to make the letter J beginning at the top. Your finger will automatically follow a clockwise route and that tells you it’s a Japanese wisteria – W. floribunda.

One of the most spectacular forms is Wisteria floribunda ‘Hon-beni’ AGM, often named ‘Rosea’. Once established, this later flowering wisteria flowers prolifically – even from a young age. The white standard petals are flushed in pink, with a yellow eye, and the keel is a deeper mauve-pink. The pink haze of flower is flattered by the emerging, bronzed foliage.

‘Shiro-noda’ AGM is highly prized in Japan for its later long racemes of scented white flowers, measuring up to two feet or 60cm in length. Like most white flowers, the accompanying foliage is a light, fresh-green when young. The combination of white flowers on wiry dark stems, and spring-green foliage captures the spirit of early summer.

There are also double-flowered forms and they include Wisteria floribunda var. violacea plena AGM.  An excellent and recent RHS monograph, Wisteria by James Compton and Chris Lane, mentions an 1878 quotation by French Botanist Élie-Abel Carrière. He described the flowers as ‘double violets on long trusses’.  Hold on to that wonderful image in your mind, although these are definitely double purple-pink violets! 

Silky wisteria, W. brachybotrys, is from southern Japan and it’s named because the leaves and flowers buds are silky to the touch. The large, strongly fragrant flowers are held on long, but broad racemes. This one has reddish-brown stems that travel in anti-clockwise direction.

Although gardeners were keen to grow Japanese wisterias, it was the arrival of Asian wisterias into Europe in 1830 that rocked the gardening world. The oldest remaining Chined wisteria, Wisteria sinensi, was planted on the walls of The Orangery at Bicton Park in Devon in 1837. Although arguments rage on about this. It was suggested by John Loudon, who was apparently potty about wisterias.

Chinese wisteria, W. sinensis, twines in an anticlockwise direction and, if you form a capital C starting at the top, your finger inevitable follows an anticlockwise route.  There is a very-free flowering, sweetly fragrant, mauve-blue May and June flowering form named ‘Prolific’ AGM. And it definitely lives up to its name. That excellent book on wisteria tells us that the first flowering Chinese wisteria grew on Charles Hampden Turner’s home, Wood Lodge, Shooters Hill, Woolwich in London.

Turner, who was a keen gardener, pioneered the use of steam heating in conservatories. He won an RHS medal for being the first to get Chinese wisteria to flower in England. His position as Deputy Chairman of the East India Docks Company, importers who had a monopoly on Chinese imports, would have allowed him early access to Chinese plants. Early introductions generally involved a ride on one of their tea clippers!

Thomas Carey Palmer, of Vale Cottage in Bromley in Kent, also acquired a Chinese wisteria and he passed a plant to a famous Hammersmith nurseryman named James Lee c. 1818. At first a wisteria plant would set you back for 6 guineas, but by the mid 1850s prices had tumbled to half a crown. Affluent gardeners across the country planted many and some of those 19^th century specimens are still belting out the flowers today.

Flowering depends on regular two-stage pruning and you’ll need a long ladder and, perhaps, a head for heights. The long whippy growth, which reaches a foot in length by July, should be trimmed back to four to six leaves towards the ripened wood. The second ‘short-back and sides’ prune occurs in February or early March, when this climber is just stirring. Leave two buds on each shoot to create a skeletal framework. This twice-yearly pruning regime lets in light and ripens the wood, encouraging more flowering spurs and fatter flower buds.

This twice-yearly prune will also keep wisterias compact, making them less prone to wind damage should gales occur.  Watch the sap when pruning, it stains your clothing a rusty brown. If you’re rejuvenating an old wisteria, tackle it in February or early March. If it’s newly planted let it go upwards and reach the desired height before making an serious cuts.

Happy gardening – Val Bourne

About the Author

Val Bourne is a multi-award-winning garden writer, hands on gardener and committed plantaholic. She manages her third of an acre garden without using chemicals – something she has always believed in. Her last book The Living Jigsaw, is all about her eco-friendly garden. She has been interested in the natural world since childhood and has actively tried to influence gardeners to be greener in order to help the survival of our planet. Val has been judging RHS plant trials for the past 16 years and she appears in many publications, including The Daily Telegraph. Val is an Ambassador for The Hardy Plant Society. She actively supports nurseries and gardens in this country.

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