Pruning wisteria (the twice-yearly technique in detail)

How to do it

1. 1Find the permanent framework first — the thick woody stems tied in along wires, trellis or a wall — and never shorten these; they're what the flowering spurs are built on.
2. 2In July-August, find this year's whippy green side-shoots growing out from the framework. Counting outward from where each shoot joins the framework, cut back to the 5th or 6th leaf, leaving roughly 30cm. Cut just above a leaf, angled, with a minimal stub.
3. 3Leave any leader shoots still being trained to extend the plant's coverage over its support — only start the twice-yearly regime once the plant has filled its allotted space.
4. 4In December-February, once the plant is bare, find those same shortened shoots (now short leafless stubs) and cut them back further, to 2-3 buds (roughly 5-10cm) from where they meet the framework.
5. 5Repeating this shortening on the same shoots every year builds up short, stubby flowering spurs along the framework — the actual flower-producing structures, the same principle as spur-pruning a fruit tree.
6. 6Feed in spring with a potassium-rich feed (sulphate of potash on poor soil, or a tomato-type feed for containers) rather than a high-nitrogen fertiliser, and water well through July-September while next year's flower buds are forming.

Plants that use it

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