Everything you’ve ever wanted to know about growing wisteria

There’s just something about the sight of wisteria’s fragrant, pendulous, giant flower clusters dangling from a high, sunny wall, pergola or house façade on a sunny day in May that induces awe and admiration as well as a pang (or two) of envy. Few plants are more seductive.

But before I succumb entirely, it’s at this point that I always have to sternly remind myself that that not only is this a climber that needs space to romp and roam, it also needs plenty of tender, thoughtful loving care, if it’s to properly flourish.

True, you can keep it relatively compact with a very regimented pruning regime. For owners of small gardens absolutely determined to enjoy the sight of its glorious May-June blooms come hell or high water, with considerable effort it can even be grown as a “standard” in a large tub or container. But to do so means ignoring the fact that the real glory of this vigorous twining climber in full, majestic blossom is the impressive scale of its display.

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Blue wisteria in Oslo, Norway. Photograph: iStock

That giant scale is one that dwarfs most other garden climbers. Given the right growing conditions, a fully mature wisteria plant can reach a height and spread of up to 12 metres, quickly scrambling up walls, pergolas, decorative tunnels, arches and mature trees by wrapping its twining, woody stems around anything that offers some form of vertical support.

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If you’re growing it on a high wall, then it’s best trained as an espalier onto a latticework of strong horizontal galvanised wires spaced 30-45cm apart and fixed securely in place. As the young stems reach upwards and outwards, they’ll need to be tied against these wires (not tucked under them) using garden twine to gently keep them in position.

While you also sometimes see wisteria planted to grow up the branches of a nearby large host tree, this is generally not a good idea. Not only does it make this climber extremely challenging to routinely prune (see below) and impact upon its flowering display, it can also cause serious damage to the host tree by suffocating its leafy canopy and overburdening it. For the same reason, forget growing wisteria on flimsy garden trellising or lightweight fencing, which the plant will slowly but surely start to topple as it matures and grows heavier.

Greedy, heat-loving, and fast-growing, wisteria likes a sheltered south or west-facing wall or structure where its emerging flowers will be protected from damaging late spring frosts (the plant itself is fully hardy) and where its twining, woody stems can slowly ripen in warm sunshine. A humus-rich, fertile, moisture-retentive but free-draining soil suits it best, ideally amended with a sprinkle of slow-release potash-rich organic fertiliser before planting and as an annual top-dressing in spring. If yours is a garden inclined to winter wetness, then it’s also a good idea to work some generous handfuls of coarse horticultural grit into the soil before planting to stop its roots sitting in cold, damp soil.

To encourage this deciduous climber to develop a good, spreading growth habit with an even distribution of flowering stems and a reliable display of its large and beautiful pendulous blooms in May-June, wisteria needs careful pruning twice a year (see below for a brief guide). This will also prevent its twining stems from obscuring windows or undermining the stability of other built structures such as drainpipes, guttering or rooftiles.

All of which tells you that this demanding, beautiful, rampageous rockstar of a plant is not for the laid-back or disorganised gardener, or for those with limited growing space. In that case, far better to admire it from afar. But if you can give it the space, the growing conditions and the tender loving care that it requires, then you’ll be the envy of many.

How to prune wisteria

Wisteria needs regular pruning twice a year to keep it in shape and encourage the plant to flower generously. In July/August, a couple of months after the flowers have faded, use a sharp secateurs to cut back any unwanted new shoots (those not needed to create the plant's woody framework of branches) to about 5-6 buds/ 30cm long. In January/February of the following year, cut these same pruned stems back again to about 2-3 buds/10cm long. For detailed specific instructions on training a wisteria against a wall as an espalier, or as a standard growing in a border or large container, or as a more free-roaming specimen on a large pergola, tunnel or arch, see rhs.org.uk/plants/wisteria/pruning-guide

Five great wisterias to grow

Wisteria sinensis 'Prolific': A classic variety of Chinese wisteria often seen gracing the high walls of old houses, its dangling racemes of strongly scented, deep violet-blue flowers appear in May/June on bare stems just before the plant comes into leaf.

Wisteria floribunda 'Lawrence': An award-winning variety of Japanese wisteria with large, scented pale lilac-blue flowers that appear in May-June when the plant is in leaf

Wisteria floribunda 'Domino': An award-winning, slightly more compact variety of Japanese wisteria, with subtly bicoloured, gently scented flowers. An elegant mix of violet and very pale lilac with a barely-there flush of primrose yellow at their centres, these appear in May-June when the plant is in leaf

Wisteria floribunda 'Alba': An ethereally beautiful variety with long, drooping, scented racemes of ghostly-white flowers that appear in May-June when the plant is in leaf.

Wisteria brachybotrys 'Showa-beni': Its romantic, pale-pink flower trusses, which appear in June, are a distinctive feature of this new variety of wisteria.

This week in the garden

Certain kinds of flowering annuals are always best direct-sown in the garden rather than being transplanted as young container-grown specimens. Examples include Californian poppies, nigella and cornflower, all of which can be direct-sown now into any bare/empty patches of soil in a sunny border/container for a late summer display of their colourful blooms. Just be very careful not to accidentally hoe/weed out the baby seedlings as they emerge, and take precautions against slug damage.

Spring-flowering bulbs growing in rough grass should be left to naturally die-back to ground level, to allow them to self-seed, as well as to fatten up below ground in preparation for next year. So resist the urge to mow and instead leave nature to do its thing.

Dates for your diary

May 22nd (9.30am-5pm), Airfield Estate, Dundrum, Dublin: Irish Specialist Nursery Association Plant Fair with a wide variety of nursery stalls selling trees, shrubs, herbaceous perennials, clematis, and garden paraphernalia, see airfield.ie

June 2nd-6th, Phoenix Park, Dublin 8: Ireland's biggest annual garden show Bloom returns to Phoenix Park with a wide variety of show gardens, a new outdoor nursery village and many other attractions , tickets from €25, see bordbiabloom.com for details and to pre-book tickets.