How to grow wisteria

Demonstrated by the RHS. This guide draws on the "Wisteria Hysteria" video produced by the Royal Horticultural Society, featuring Becky Mealy. The RHS is the UK's leading gardening charity and the video covers training, pruning, and troubleshooting with clear demonstrations - particularly useful for anyone who's inherited a wisteria and isn't quite sure what state it's in.

1. Choose a grafted plant, not a seedling

Buy a grafted wisteria rather than a seed-grown plant. Grafted plants flower reliably after a few years; seed-grown plants can take ten years or more to produce a single bloom - if they ever do. You can identify a grafted plant by the slight swelling or bump near the base of the stem where it joins the rootstock.

The two most widely grown species in the UK are Wisteria sinensis (Chinese wisteria, with flowers opening before the leaves) and Wisteria floribunda (Japanese wisteria, with longer racemes and leaves appearing with the flowers). Both do well in UK gardens. Popular varieties include Wisteria sinensis 'Prolific' and Wisteria floribunda 'Multijuga', which has racemes that can reach 90 cm.

2. Plant in a sunny, sheltered spot

Wisteria needs full sun - ideally at least six hours a day. A south- or west-facing wall is the classic choice and works very well in East Kent's climate. North-facing walls rarely produce good flowering.

The soil should be fertile, moist but well-drained. Dig in plenty of compost before planting. Plant in spring or autumn, and position the root ball about 30 cm from the wall so it gets some rainfall rather than sitting in the drier soil right next to the brickwork. Water generously through the first growing season.

3. Fix horizontal wires before you plant

Wisteria is heavy once established - potentially very heavy. Fix substantial horizontal wires to the wall before planting, using vine eyes screwed firmly into the mortar, spaced about 30–45 cm apart vertically. Use 3 mm galvanised wire and keep it taut.

Putting up the wire support after the plant is established is genuinely awkward. Far easier to do it on a bare wall. The plant can then be trained against the wires from the start, which makes managing its shape much more straightforward.

4. Train the main stems in the first two or three years

For the first couple of years, focus on establishing the framework rather than worrying about flowers. Tie in the main stems horizontally along the wires, spacing them evenly. Encourage new lateral shoots to fill the framework. The aim is a permanent woody structure spreading across the wall, from which flowering spurs will develop.

Tie in new growth loosely with soft garden twine. Wisteria twines naturally, which is a help and a hindrance - useful for getting it to fill gaps, but you need to keep checking it hasn't wound itself around anything it shouldn't have, like guttering or window frames.

5. Prune twice a year - August and February

This is the part most people miss, and it's the main reason wisterias don't flower. The two-cut method is straightforward once you've done it once.

In August (summer pruning): cut back all the long whippy new shoots produced that summer to about five or six leaves from the main framework. This redirects the plant's energy into the flower buds rather than more stem growth.

In February (winter pruning): cut the same shoots back again, this time to just two or three buds. Those short fat spurs are what produce the flowers in May and June. Don't skip the winter cut - it's the one that really makes the difference.

6. Feed carefully in spring

Avoid high-nitrogen feeds, which push leafy growth at the expense of flowers. Use a balanced fertiliser or a specialist flowering plant feed in spring. Potassium (the K in the NPK ratio) encourages flowering, so a tomato fertiliser used according to the pack instructions is actually a reasonable choice for wisteria.

Mulching around the base in spring with well-rotted compost helps retain moisture and gradually improves the soil. Keep it away from the main stem.

7. Why it won't flower - and what to do

If your wisteria won't flower despite being a few years old, the most likely culprits are: it hasn't been pruned (or was pruned at the wrong time), it was grown from seed, it's not getting enough sun, or it's been fed too much nitrogen.

Try the twice-yearly pruning for a full year before concluding there's a more serious problem. A phosphorus-rich fertiliser in late spring can sometimes jolt a reluctant plant into bloom. That said, some plants bought cheaply as seedlings simply never perform - at some point it may be worth replacing with a confirmed grafted variety.

When to call a handyman

Fixing vine eyes and wires to brickwork or render is a job that needs the right fixings and a decent drill. On older walls, especially in some of the older properties around Sandwich, you want to be sure the fixings are properly anchored before something as heavy as a mature wisteria is attached. Richard can put in a proper wire system, and sort out any wall fixings that have been done badly in the past.