Know Your Shrub, Know Its Wood

Pruning is far less mysterious once you understand one simple idea: a shrub flowers either on growth it made last year, or on growth it makes this year. Get that right and most of the calendar falls into place. Cut a forsythia in November and you will remove the flower buds that would have lit up March. Cut a buddleja in June and you lose the current season's blooms on the very wood carrying them.

So divide your shrubs mentally into two camps. Group one flowers on old wood — think forsythia, philadelphus, weigela, deutzia, flowering currant and most early-flowering viburnums. Prune these straight after flowering. Group two flowers on new wood — buddleja, caryopteris, hydrangea paniculata, perovskia, hardy fuchsias and cornus grown for winter stems. Prune these in late winter or early spring, before growth restarts.

Whatever you do, work with sharp bypass secateurs, make cuts cleanly, and keep the three Ds in mind: dead, damaged and diseased wood comes out first, every time.

March and April: Pruning for Summer Flowers

This is the month for the hard-pruning mob. As buds begin to swell but before leaves unfurl, buddleja davidii can be cut back to a low framework of 60–90cm (2–3ft) from the ground. It looks brutal; the resulting arching stems and cone-shaped flower spikes are worth it. Do the same for caryopteris, cutting to about 30cm, and for perovskia down to a permanent woody base.

Cornus alba and Cornus stolonifera, grown for their coloured winter stems, are cut hard in March — to within 5–7cm of the previous cut — to trigger the vivid young growth that gives the best colour. Hydrangea paniculata varieties are trimmed back to a strong framework, removing thin twiggy growth entirely.

• Cut buddleja, caryopteris, perovskia and hardy fuchsia hard as buds break.
• Coppice dogwood and willow for fresh winter stems.
• Remove the oldest one in three stems from overgrown deciduous shrubs.
• Hold off on anything marginally tender until the risk of hard frost has passed.

Finish with a generous mulch of well-rotted organic matter, kept clear of the stems, and the plants will repay you within weeks.

May and June: The Post-Flowering Window

As spring blossom fades, the old-wood group comes into play. Prune forsythia, ribes, spiraea, kerria and flowering currant within a few weeks of the flowers dropping — ideally by mid-June. The rule of thumb is to remove up to a third of the oldest stems at the base, then shorten the remaining flowering stems by about a quarter to encourage bushy regrowth.

Philadelphus, weigela and deutzia follow the same pattern. If you leave it until July, you are cutting into next year's flowering wood and the following spring will be thin.

Evergreens such as choisya and escallonia can also be trimmed lightly now, once flowering has finished. Keep the clippings if you have a hedgehog-friendly corner, and avoid trimming in the heat of the day during a dry spell — stressed plants recover poorly.

July and August: Shaping, Deadheading and Lavender

Midsummer is about maintenance rather than surgery. Deadhead roses, repeat-flowering shrubs and perennials to keep energy going into roots and new blooms. Clip lavender immediately after flowering — cutting back into the soft green growth but never into the old bare wood, which rarely regenerates.

Wall shrubs and climbing ornamentals can be tied in and thinned now, letting air move through the canopy. In woodland-edge planting, this is the moment to lift low branches of hazel and field maple so underplanted shade-lovers still get light without losing shelter.

If you are renovating an overgrown shrub, midsummer after flowering is a gentler time to do it than deep winter, as regrowth is rapid and the plant can heal quickly.

September to November: Tidy Without Cutting Too Deep

Autumn is for clearing rather than clipping. Cut out any dead, crossed or rubbing branches you have spotted through the season, and remove spent flower heads from hydrangeas only if you prefer a neat silhouette — many gardeners leave them for frost interest and wildlife cover.

Leave the seedheads standing where you can. They feed finches through winter and shelter overwintering insects, which in turn feed the birds that patrol your woodland garden come spring.

• Tidy fallen leaves beneath shrubs and add them to a leaf-mould bin.
• Avoid pruning evergreens after early September — new growth will not harden off.
• Do not prune in wet weather; open wounds invite fungal problems.
• Sharpen and oil your tools before putting them away for winter.

December to February: Dormant Pruning and Renovation

Once the leaves are down and the sap is still, you can see the structure of a shrub properly. This is the season for renovation: removing old, congested wood, thinning dense centres and reshaping neglected specimens. Tackle one major branch a year on mature shrubs rather than cutting everything at once.

Hardy deciduous subjects — including most woodland shrubs, hazel, dogwood and willow — tolerate winter work well. Leave anything tender, and anything flowering on old wood, strictly alone. Also avoid pruning in hard frost, when brittle wood shatters rather than cuts cleanly.

Winter is the perfect time to plan. Walk the garden with a notebook, photograph the bare framework of your shrubs, and mark which ones flowered where. By the time March arrives and the buddleja is calling, you will know exactly which stems to cut and which to spare — and your shrubs will flower better for it, season after season.