How to grow and care for Wisteria
Long clusters of pendulous flowers in spring, bushy verdant foliage throughout summer and impressive woody helixes during the winter. A mature wisteria is certainly an impressive sight.
Historically Wisteria was grown as a symbol of long-life and immortality – and there is no wonder it has gained such an illustrious reputation, with one of the oldest known Wisteria trees aged around 1200 years old. A relatively easy climber to grow, keen to climb and spread. However, achieving flowers can be slightly more challenging. Therefore, brushing up on your knowledge of how to grow and care for Wisteria is sure to bring many beautiful blooms for decades to come.
Choosing a Wisteria
Wisteria vines grow from tendrils that corkscrew upwards towards the sun. They are ideal climbers for south-facing walls, pergolas and arches. Wisteria is a vigorous deciduous climber with twining stems that produce long racemes of flowers in spring and early summer. Beautifully scented they can reach around 10 metres tall. The most commonly found varieties of Wisteria are the W.floribunda and W. Brachybotrys, both native to Japan, and the W. Sinensis from China. When it comes to choosing which variety is best for you, it all comes down to positioning, colour and size.
This Japanese beauty has the longest racemes of all varieties, with some measuring up to 4feet in length, blossoming in the early summer. A clockwise twining desire that carries nutrients to bear flowers and leaves at the same time of year.
The spectacular Chinese Wisteria Sinensis flowers in the late spring, signalling the arrival of impending leaves that appear in the summer. An anticlockwise twiner by comparison with shorter flower sprays of around 1 foot long.
Also known as the ‘silky wisteria’. Of the 3 varieties, the Brachybotrys has shorter cascades of flowers, with racemes growing to around 4 inches long.
When buying any wisteria, ensure that the plant has been grafted and not grown from seed. Any seed-grown Wisterias will not flower for around 20 years, if at all, so look out for a bulge at the base of the plant as evidence of grafting.
How to plant a wisteria
The best time of year for planting a Wisteria is in Autumn or early spring when they are dormant but the ground is soft. Although wisteria can happily grow in part shaded areas, they prefer full sun. It is ideal to plant them along a west or south-facing aspect, to ensure substantial flowering.
Wisterias are fairly resilient, able to thrive in a variety of well-drained soils. Once you’ve found the ideal location ensures that there are adequate supports available, such as trellis, pergolas, arches, walls and wires. Avoid corkscrewing the vines around supports. Instead, encourage them to twine parallel to their supports and glide across the surface.
Once a wisteria has been planted, it isn’t ideal to move them, as it can discourage flowering the following season. They also develop very strong woody roots, so ensure they are planted in their permanent location from the outset.
How to care and prune a wisteria
As a general rule, pruning wisteria helps to encourage flowering. So a newly planted or young wisteria does not require pruning until it has covered the desired surface area of your wall, pergola or trellis. In the formative years of its growth, these shoots will help to develop that lush, vibrant coverage that will carry plenty of flowers.
However, an older and more established wisteria should be pruned twice a year to keep it rewarding you with beautiful blooms. Simply off any wispy, leaf-less stems in July/August, down to the next cluster of 5/6 leaves. This allows the wood to ripen over the coming months to improve the chances of flower buds. Then again in February, shorten these shoots to two or three buds and tidy the plant before a new growing season begins.
In the summer months, be sure to keep your wisteria well-watered, particularly newly planted or younger plants. To keep these vigorous climbers flowering prolifically The Royal horticultural society recommends feeding your wisteria with Growmore or Fish, Blood and Bone. If planted in sandy soils with low potassium levels, “also apply sulphate of potash at 20g per sq m (1/2 oz per sq yd). You can also use a rose or flowering shrub fertilisers.”
What to do if your wisteria is not flowering
For the most part, growing a happy and healthy wisteria is relatively simple. They are a hardy, determined plant, content with climbing and produces stunning fluttering leaves with little intervention. However, a common problem with wisteria is encouraging flowers to bloom.
One of these reasons your wisteria may not be producing flowers is simple due to its age. Young wisterias on average take 15 – 20 years before they produce their first flowers. A difficult wait for even the most patient of gardeners. If however, your wisteria was in bloom when you bought it, or have blossomed previously, check your pruning technique and timing. If your timing is off then it may disrupt the formation of flowers in the following year. If your pruning too harshly you may be removing shoots and buds that will carry flowers in the upcoming year.
Ensure your wisteria is receiving enough sunlight and water? Although it may be planted against the south-facing wall of your home, check that no nearby trees could be blocking its sun exposure. As these plants enjoy bathing in full sunlight, they also tend to live in borders and soils that are prone to drought, so make sure your wisteria is receiving regular watering during any dry, warm weather. A shortage of water will affect any bud formations for the following year.
Late spring frosts can also impact flowering, as they may damage developing flowers and cause buds to drop before they open. Often this cannot be helped and one of the many reasons a flowering wisteria is so enigmatic, however, you can minimise the risk by planting beside a brick wall of your home, rather than unheated outbuildings and exposed archways, as the warmth from the brickwork and any slight heat loss from your home can create a microclimate for growth. Raising the temperature by a degree or two could make all the difference.
Finally, soils short of potassium are another common issue, a simple potash feed will help to promote flower formation for the following year.