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Start With the Structure, Not the Plant

A wooden pergola is a frame first and a garden feature second. Before you fall for the first glossy photo of a wisteria-clad arbour, think about what your timber can actually carry, which way it faces, and how much pruning you are honestly prepared to do each year. Get those three things right and the plant will do the rest.

Standard pergolas built from 100mm posts and substantial cross beams will happily take most climbers. Slimmer, decorative kits — the sort sold as a lightweight rose arch or a budget veranda frame — will not. A mature wisteria can weigh as much as a small car once the wood has thickened, and it will happily twist a flimsy rafter out of shape. If your structure is on the light side, choose clematis, jasmine or an annual climber instead.

Whatever you plant, keep the main stem at least 45cm away from the posts and train it in on horizontal wires or a fixed trellis panel. That gap lets air move around the timber, keeps the wood dry, and means you can still reach the posts to sand and re-treat them. Timber that stays permanently damp under a mat of stems will rot long before its time.

Wisteria: Beautiful, Heavy and Demanding

Wisteria is the classic pergola plant and, in the right spot, nothing else comes close. It also demands the most. Give it full sun — a south- or west-facing situation with at least six hours of direct light — and a deep, fertile, well-drained soil. In shade it will grow lush and leafy and refuse to flower.

The flowering trick is summer pruning. In August, shorten the long, whippy growths back to about five or six buds from the main framework. Then in January or February, cut those same spurs back again to two or three buds. That double chop is what concentrates the plant's energy into flower buds rather than foliage. Feed with a high-potash tomato-type fertiliser from late spring, and go easy on nitrogen-rich feeds, which simply make more leaves.

Keep an eye on gutters, downpipes and roof edges — wisteria will find them. If you want the look without the labour, a climbing rose or a honeysuckle gives you scent and colour on a much lighter frame.

Jasmine: Fast, Fragrant and Easier Going

Summer jasmine is the one most people mean when they talk about a scented pergola. It is semi-evergreen in mild areas, throws out creamy white flowers from midsummer, and releases its perfume in the evening. Give it a sunny, sheltered spot and it will romp away in a season.

Prune it straight after flowering, thinning out congested growth and shortening side shoots. It flowers on the previous year's wood, so a hard spring chop will cost you a year of scent. In colder gardens, some top growth may be cut back by frost; simply tidy the damaged stems in late spring once new shoots appear.

Winter jasmine is a different beast — yellow flowers on bare stems in January and February, but it is a scrambler rather than a true climber, so it needs tying in regularly. Star jasmine is evergreen and glossy but only reliably hardy in milder parts of the country, where it wants sun, shelter and a free-draining soil.

Clematis: The Most Versatile Choice

Clematis suits almost every aspect and every pergola, provided you know which pruning group you have bought. Get this wrong and you either lose a year's flowers or end up with a tangled mess.

• Group 1 — Montana, alpina and armandii types. They flower in spring on old wood, so prune only after flowering, and lightly. Montana is vigorous; on a small pergola it will smother everything.
• Group 2 — large-flowered early types. They bloom in late spring and often again later. Prune lightly in late February, cutting back to a strong pair of buds.
• Group 3 — viticella, tangutica and late large-flowered varieties. They flower on new growth from midsummer. Cut the whole plant back hard to about 30cm in February or March.

Clematis follow one golden rule: head in sun, feet in shade. Plant it deeply, with the crown 5–8cm below soil level, to reduce the risk of clematis wilt, and shade the root zone with low-growing perennials or a few flat stones.

Matching Plant to Aspect and Soil

Sunny, south- or west-facing pergolas take wisteria, star jasmine, most clematis and ornamental vines. North- and east-facing structures are trickier but not hopeless — clematis montana, akebia, climbing hydrangea and ivy will all cope with cooler, shadier conditions.

Most climbers prefer a fertile, well-drained soil, neutral to slightly alkaline. Improve heavy clay with compost and grit before planting, and never let the roots sit in water. Clematis in particular resents waterlogging. Wisteria wants depth, so dig a generous hole and work in plenty of organic matter.

Water thoroughly for the first two summers while the roots establish. Mulch in spring, but keep the mulch clear of the stems so it does not soften the bark.

Keeping It Manageable Year After Year

Decide on a framework early. Guide two or three main stems along the wires, then train the side shoots vertically. Tie in with soft twine or rubber ties, and check them each spring — bindings left too long will cut into swelling stems.

Feed for flowers, not foliage: a high-potash liquid feed from early summer suits wisteria and clematis alike. Watch for aphids on soft new growth, and be alert to clematis wilt, which causes sudden collapse of a shoot — cut it out below the affected area and the plant usually recovers.

Finally, look after the wood. Check fixings each spring, re-treat any bare patches, and keep stems off the timber wherever you can. A pergola under a well-chosen climber is a wonderful thing, but it lasts far longer when you can still see the frame beneath the flowers.