Wisteria (Wisteria) is a woody, deciduous climber that reaches 8 to 12 metres and flowers in May and June with hanging racemes in blue violet. It is hardy across most of the UK and northern Europe, but it needs a south or west facing position to set buds. Two things decide whether a plant flowers or only grows: whether it was grafted or raised from seed, and whether it is pruned twice a year instead of once.
Grafted or seed raised decides when the plant flowers
The most common question about wisteria is why the plant does not flower, and the answer usually lies back at the nursery. A wisteria raised from seed passes through a long juvenile stage before it becomes capable of flowering, and that can take up to 20 years. A grafted specimen carries a shoot from a plant that already flowers, and it usually blooms within three to four years of planting. Same species and same care, but fifteen years of difference in waiting time.
The graft union: A grafted wisteria has a knob or a clear swelling on the stem a little way above soil level, where the cultivar sits on the rootstock. A seed raised plant has a smooth stem all the way down into the pot.
The label: Plants with a cultivar name in single quotes, such as 'Prolific', 'Amethyst' or 'Multijuga', are nearly always grafted. If the label says only Wisteria sinensis with no cultivar name, the plant is more often seed raised.
The flowers: A plant in bloom answers the question on the spot.
If your plant puts on several metres a year without flowering and the base of the stem is smooth, seed raising is the likely explanation.
Pruning in two rounds
Wisteria is pruned twice a year, unlike clematis where one cut is enough, and pruning is the most important job of all. The flowers do not sit on the long new whips but on short side shoots, spurs, that are built up over several seasons. The whole point of pruning is to turn this year's long shoots into such spurs.
July or August: Shorten all of this year's long shoots to five or six leaves, about 30 cm. The shoots you are keeping for the framework are left uncut and tied in. The cut slows extension growth while the plant still has all of late summer ahead of it, so the strength goes into forming buds instead of into new metres of whip. At the same time light reaches the wood, which ripens better.
January or February: Go back to the same shoots and cut them to two or three buds, about 10 cm. The plant stands bare and the buds are visible: flower buds are round and fat, leaf buds narrower and flatter. Cut just above a bud and remove shoots that grow in towards the wall or cross one another.
Without the summer cut you get a tangled mass of leaves at the top and few racemes. Without the winter cut the racemes end up further and further from the framework, where the foliage hides them. The effect shows the following year, so allow two seasons before a neglected plant responds.
Japanese and Chinese wisteria
The species differ in the length of the racemes, in when the flowers come in relation to the leaves, and in which way the shoots twine. The twining direction can be read all year round, even on a plant that has never flowered. Look from above at a young shoot where it winds around its support.
| Species | Twines | Racemes | Flowering and leaves | Height |
|---|---|---|---|---|
| Japanese wisteria (Wisteria floribunda) | Clockwise seen from above | The longest in the genus, up to 1.2 m on 'Multijuga' | Flowers at the same time as the leaves come out | 8 to 12 m |
| Chinese wisteria (Wisteria sinensis) | Anticlockwise seen from above | 15 to 30 cm, the whole raceme opens at once | Flowers before the leaves break, the racemes hang unobscured | Over 12 m |
Both are sweetly scented with a note of grape. The long Japanese racemes come into their own over a pergola, where they hang free. Against a house wall Chinese wisteria suits better, because the short racemes are not pressed in against the wall.
The support has to carry a mature plant
Wisteria is a twining climber, just like honeysuckle, but in a different weight class. The whole stem winds around whatever is nearest and then turns woody. An old plant has stems as thick as a small tree trunk, and the grip tightens every year because the stem thickens while the spiral cannot widen. That is why wisteria crushes downpipes, picket fences and cladding.
Against a wall: Run heavy galvanised steel wire horizontally with 30 cm between the wires and fix it with 7.5 cm vine eyes, so that the wire stands clear of the wall. A straining bolt on each wire lets you retension it when it slackens. Screw into a stud or into masonry, never into render or surface cladding alone.
Building details: Lead the shoots away from gutters, downpipes and eaves while they are soft and green. A shoot that has managed one turn around a downpipe cannot be freed three years later without the pipe breaking.
Tying in: Tie loosely with soft ties and check the ties every spring. String left in place cuts into the stem as it thickens.
Freestanding: A trellis of 15 to 25 mm battens is enough for an annual climber but not for wisteria. Dimensions and anchoring are covered in the guide on building a trellis.
Position, soil and planting
Wisteria flowers in sun and sets few or no buds in deep shade. Choose a south or west facing wall with sun for most of the day and a fertile, well drained soil. Plant between October and April if you can. Set the plant 30 to 45 cm out from the base of the wall and angle the rootball in towards the support, because the ground closest to a house wall lies in a rain shadow. In a container the pot needs to be at least 45 cm across.
For the first three or four years the plant rarely covers the whole support. If you want flowers on the wall in the first summer, sow an annual climber alongside, for example sweet peas or cup and saucer vine. Low perennials at the foot of the plant shade the soil without competing with the rootball.
Watering and feeding
Water in July, August and September: That is when next year's flower buds are formed. If the plant dries out in those months you lose the following year's flowering, even if it looks undamaged.
Potassium ahead of nitrogen: A nitrogen rich feed gives more whip and fewer flowers. On light sandy soil, give a potassium feed in spring instead, about 20 g per square metre.
Suckers: Remove shoots that come from the rootstock below the graft union. They grow more strongly than the cultivar above and they do not flower.
Hardiness and spring frost
Hardiness ratings cover the plant's survival, not its flowering. The plant itself is tougher than its flower buds, and it is that difference which decides how often you get to see the display. A frosty night in April or May, once the buds have swollen, can wipe out a whole year's racemes on a plant that came through winter without a mark. Avoid frost pockets where cold air collects at night. A sunlit wall stores heat during the day and evens out the night temperature, which is one reason wisteria is grown against a wall and not in the open.
Wisteria is poisonous to eat
Every part of the plant contains the glycoside wisterin along with lectins, and the concentration is highest in the seeds. The pods are flat, brown and velvety, grow 5 to 10 cm long and hold a few seeds of around 1 cm. They split open and twist as they dry, and empty pods often stay on the plant into winter.
Eating them causes nausea, vomiting, stomach pain and diarrhoea, and wisteria has caused poisonings in children in several countries. That is no reason to do without the plant, but if small children use the garden it makes sense to cut the pods off before they open. Do not confuse wisteria with laburnum (Laburnum) either, a small tree with yellow racemes whose seeds contain cytisine.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-09-03