Prune sap-rich trees now

DECEMBER is the best month for pruning trees or shrubs which might bleed sap. Most woody plants heal rapidly after pruning and lose no sap. But grape vines, silver birches, maples and a few others can bleed. Freshly cut stumps may ooze for days, weakening plants.

To minimise bleeding, prune such trees, shrubs or climbers when they are at their most dormant — usually between November and Christmas.

Use clean tools to avoid spreading infections. Make clear cuts at right angles to the stems to minimise wounds. Binding, painting or dressing the wounds is unnecessary. It’s better if they can dry rapidly and then begin healing.

Prune plants only if absolutely necessary. Birches, in particular, look best if they can grow as naturally as possible. If you do have to prune, thin the branches, rather than shortening them all and spoiling the tree’s outline.

With birch and maples whose bark is attractive, the prunings could be valuable as cut material. Birch bark makes a delightful foil to dark evergreen foliage or silver decorations at Christmas.

If you grow grapes on a wall, prune back to the basic framework of the plant. Yield will be best if you can prune side-shoots back to the main laterals or ‘rods’.

Free-standing outdoor grapes are usually grown as cordons. Best-known is the Guyot system — a posh term for double cordons. The vines are grown with an upright, short main stem which carries two lateral branches, usually trained in a flattened Y-shape. Fruits develop on stems that grow from those side-shoots.