Diarmuid Gavin: Dreamy wisteria
Coaxing a performance from this star of the garden is well worth the effort
Some stars arrive from the US with massive entourages, they travel in cavalcades of blacked-out limousines and demand litters of newborn puppies to play with, or that the blue M&Ms being removed from their bowl of confectionery. Why? Because they can... and because they are perceived as being worth it. Once they begin to sing, all is forgiven.
And garden plants can act in a similar way. Take for example a star that's set to shine in our gardens over the next month - wisteria! This stunning Oriental species can, from time to time, show an ugly side. The seed pods are poisonous so be careful if there are children around.
It can be reluctant, stubborn - sitting staring at hopeful gardeners for years - demanding of attention, requiring the best of fertiliser and a good drink, while refusing for years on end to reveal its beauty. But upon its first show, and every year thereafter, its wondrous display of pink, lilac, white or purple is quite rightly revered and applauded.
It can take seven years to coax this performance from straggly stems. But for drama, colour, and fragrance in one package, nothing can beat wisteria. It can beautify the plainest of buildings and is nectar to the eyes.
So, what are its requirements?
Well, firstly, it is not self-supporting - its stems need a support to twine around. And this needs to be something very solid as, when it takes off, wisteria can be rampant and very heavy. So plant where it has space to grow, preferably in full sun.
As a member of the legume family, its root nodules have nitrogen-fixing capacity so don't go heavy on nitrogen feeds - this will just lead to too much vigorous sappy green growth. Choose feeds such as tomato that are higher in potash, and a balanced dollop of well-rotted manure every spring will help keep roots well-nourished and protected.
Good blossoms are also the result of a twice-yearly pruning regime. During late winter, cut back hard to two or three buds. The second pruning takes place in August when buds are developing - by shortening leafy shoots, you will encourage bud development. It is also important at this time that the plant is not subject to drought when the buds are forming, so keep an eye on its watering needs especially from July to September. The reward is the glorious long racemes of white, pink, blue or mauve pea-like flowers in May and June. The most popular is Wisteria sinensis, the Chinese wisteria - this twines anticlockwise and the fragrant mauve or lilac flowers blossom before its leaves appear. The Japanese wisteria, W. floribunda, twines around supports in a clockwise direction and you will find blossoms and leaves at the same time.
I have used it as the primary plant to scramble up the cast-iron supporting pillars of my verandah and, for all the waiting, it's put on an annual performance of pure magnificence.
There are two places that spring to mind if you wish to see these plants in their prime in Ireland. It's a celebrated species in the Botanic Gardens in Glasnevin, Dublin. But perhaps even more exotic are those in the gardens of Bantry House in Cork, where their host structure has a fountain as its centrepiece and sits at the base of the '100 steps to heaven', the start point for your celestial journey!
In short, wisteria will be the plant that keeps on giving…eventually. You have to provide it with what it loves. Create some support and it will reward you as a wonderful classic garden plant, climbing to new heights and impressing all who see it.