Ask the Gardener: Wisteria

GROWN for its green feathery foliage and drooping scented flowers, Wisteria is one of the most spectacular and sought after of all garden plants.

Because it brings such an exotic touch to the garden with its thick snake-like stems and lovely scented trailing flowers, many people believe they are delicate and hard to grow. However, this is not the case. Given the correct growing conditions and provided one has enough space, Wisteria are surprisingly easy to grow and maintain.

A member of the pea family, Wisteria is a deciduous climbers with pea-like flowers in colours of white, pink, lilac and blue. It can be grown as a tree but its flowers are best seen trailing down a wall or hanging from an arch or pergola. When growing on a wall try to encourage a main stem and use strong lengths of wire on which to train the branches. The two species mainly grown in Ireland are W floribunda which comes from Japan and W sinensis, a native of China. Both species are tough but W sinensis tends to flower earlier than W floribunda and can be affected by late winter frosts.

Wisteria sinensis does however grow taller and can produce a second flush of flowers in late summer, in those years when we do get a summer!

Q. I have an old shed, the wall is 12ft high and 12ft wide, would this be sufficient to grow wisteria on?

A. Wisteria can reach a height and spread of 30ft, so it needs a good size structure to grow it at its best, but 12ft by 12ft is fine. It is big enough to allow the snake like stems to develop and thicken so they can be appreciated even in winter when the wisteria has lost its leaves.

Q. What is the best site for growing Wisteria?

A. Rich soil in full sun gives best results, but it will grow in most soils as long as it is not wet clay.

Q. I have wisteria growing on a sunny sheltered wall for the last five years and it has not flowered. The soil is good and every year it produces leaves but still no flowers what am I doing wrong?

A. Wisteria is unlikely to flower in its first few years as it takes time to establish, once established it will produce a few flowers the first year and more will appear with each passing year. Wisteria grown from seed can take decades to bloom so it is best to buy grafted cultivars.

Another reason for not flowering could be that you are giving the plant too much nitrogen which encourages leaf growth and inhibits flowering. I would suggest feeding it with phosphate or potassium which encourages flower growth only.

Q. How do I go about pruning Wisteria?

A. Long shoots should be trimmed back to about six buds from the central stem in July and to about three buds in late Winter/early Spring depending on the weather.

* If you have any gardening questions, you can contact Charlie by visiting www.thepavilion.ie, facebook.com/thepavilioncork , or via twitter @the_pavilion


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