Pruning guide & shrubs

JENNIFER STACKHOUSE o ers two simple rules for pruning just about any flowering shrub in your garden, with plenty of tips to get it right

For many gardeners the thought of pruning a plant causes stress and doubt. Questions crowd in as you stand there, secateurs in hand. When is the right time to prune? How much should I prune? Which part of the plant do I prune? Will I kill my plant? Will it ever flower again?

The first rule of pruning is, don’t panic! The second rule is to understand why you are pruning. If you follow these two rules, you can prune with confidence.

WHY & WHEN TO PRUNE

Pruning is undertaken to shape a plant, remove dead growth and to encourage new growth and flowers. Shaping and removing dead growth can be done throughout the year, as needed.

Shape a plant by removing growth that is in the wrong place (such as a stem that’s growing into another plant or another branch on the same plant), cutting away low or wayward growth, or taking off inward-facing branches. Plant shaping also includes pruning that’s done to form a hedge, topiary, standard or espalier.

Pruning to encourage new growth is usually done after flowering (or after fruiting if the plant is productive or has ornamental berries). Pruning after a plant has flowered eliminates the risk of pruning at the wrong time and accidentally cutting off any stems that were about to flower.

Dormant plants that flower on new wood, especially roses, are pruned in winter after they have dropped their leaves and before they begin to regrow. The new growth that’s stimulated by pruning produces flower buds.

HOW MUCH?

The amount that’s pruned away varies depending on the plant and the reason it is being pruned. However, a good rule of thumb is to not prune a woody plant such as a shrub by more than a third of its overall growth at any one time. Herbaceous perennials can be cut to the ground to regenerate.

Much of the pruning gardeners do on a regular basis consists of cutting off just small amounts of growth. Deadheading (that is, pruning off dead flowers) removes spent blooms and so prevents seeds forming. Tip-pruning, which is nipping out the growing tip, encourages bushy growth. Annuals and hedging plants are good subjects to tip-prune, as this results in bushier plants.

A much harder prune is done to regenerate a plant or to encourage lots of new growth from its base. Hard-pruning is successful when plants can regrow from old growth or readily produce new growth from their base. When the aim of pruning is to stimulate new growth from the base of the plant, older stems (usually three years old) are removed by completely pruning them off at the base of the plant (see 'Renovate a cane-type shrub' step-by-step on page 42).

Occasionally hard-pruning can kill a plant (lavenders, daisies and most conifers do not respond well to hard-pruning). To check how a plant may respond to pruning, do a test.

Cut back part of it and see how it regrows before pruning further.

WHERE TO CUT

Cutting a plant will encourage new growth, so cut back to just above a node (a growth point on the stem). In this way, the new growth will cover the pruning cut. To shape the direction of growth, cut back to a growth point

that’s going to shoot in the direction that you want it to, for example, outwards.

After you have pruned, check back from time to time to look for new growth. When plants are actively growing (spring to early autumn), new growth will appear within weeks of pruning. As pruning encourages new growth, it is important to feed and water plants that have been pruned as the new growth begins. Keep supplying regular water as the growth develops. WARNING! Avoid pruning frost-tender plants during late autumn or winter as pruning may encourage new growth that may be damaged by cold. Delay pruning these plants until the weather warms.

PRUNING TOOLS

Use clean, sharp secateurs to prune small growth. For thicker growth that’s too large for secateur blades (usually above 2cm in diameter), use either loppers or a pruning saw. Where there's lots of material to prune – for example, on a hedge – use shears or a powered hedge trimmer. Prune growth that’s difficult to reach with a pole pruner. Turn to page 40 for more information on which pruning tools to choose.