How to prune spring-flowering shrubs

The bright yellow blossoms of forsythia and the fragrant purple sprigs of lilacs are welcome springtime sights. Shrubs such as these launch the seasonal flower display with fireworks of colour. Here are some TLC tips to ensure that those glorious bursts of colour reappear year after year.

Prune for blooms, beauty and health
Judicious pruning keeps shrubs blooming their best. Cutting off spent flowers diverts the plant’s energy from unnecessary seed production to the creation of plentiful flower buds for next year. Pruning can also improve the shape and structure of a bush, enhancing its beauty and keeping it healthy by improving air circulation and allowing sunlight to penetrate into the centre of the clump. And because many spring-flowering shrubs produce flowers on new wood, pruning out old branches promotes the growth of young, blossom-bearing ones. However, shrubs younger than three years generally do not need pruning.

Use the right tools
Most shrubs can be pruned using one or more of four basic tools: a pair of secateurs, loppers, a small pruning saw and pole-mounted pruners. For twigs and stems measuring less than the diameter of a thumb, hand-held secateurs will do the job. Loppers, ratcheted for better leverage, can handle thicker stems. Large branches may require a Japanese pruning saw, which cuts on both the pull and the push strokes, making them more efficient than saws fitted with conventional blades. For cutting high branches, pruners mounted on an extensible pole make it easy to reach to the top without a ladder.

The blades of secateurs and loppers should be sharpened and honed after every few cuts. When pruning out diseased branches, sterilize blades with rubbing alcohol after each cut.
Know when to prune
Spring-flowering shrubs are able to bloom so early in the season because they produce their flower buds during the previous season. Forsythias, for example, start forming flower buds over the summer, and these nestle behind leaf axils where they remain dormant through fall and winter.

To prevent the removal of next season’s flower buds, it’s best to prune before the buds start to develop. Various shrubs produce buds at different times of the season, and climate plays a role, too, so it’s often difficult to gauge just when this will happen. Therefore, the safest time to prune is just after the shrub has finished blooming.

How to prune step by step
Here’s how to prune most spring-flowering shrubs, including serviceberry, deutzia, forsythia, beautybush, honeysuckle, mock orange, lilac and weigela.

Remove any dead or diseased wood, cutting stems right to the ground.
Prune out some of the older branches (these are thicker and darker than younger stems), cutting them back to about 30 centimetres from the ground.
Shorten the remaining stems by about one-third and remove any inward-facing branches. This will control the size of the shrub and open it up to air and sunlight.
Remove any remaining dead blossoms; depending on the shrub, these can be removed by shearing, pruning or manually snapping them off.
Pruning shrubs in this manner every year, being careful not to remove more than one-third of the overall size, ensures attractive, floriferous and healthy plants.
Read more in How to and Techniques

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