When to prune rhododendrons

Not sure when to prune rhododendrons? Don’t worry, this guide is packed with expert tips so you can confidently keep these backyard shrubs healthy and looking their very best.  

On the desirable evergreen shrubs, with glossy evergreen leaves, these sturdy woodland plants put on a stunning display every spring and early summer with their mass of vivid blooms. In endless shades of white, and peach through to the deepest pink, purple and red the starry, trumpet-style flowers are rich in nectar and hugely valuable to pollinators too. 

Left to their own devices though, these plants can quickly get out of hand – indeed they are known to be invasive in some areas – so learning when to prune these backyard favorites is essential for keeping them in check.

So, whether you want to bring an unruly rhododendron back under control or just keep existing plants in the best possible shape, this easy-to-follow guide is for you.

When to prune rhododendrons

When growing rhododendrons, it is also important that you know when to prune rhododendrons.

This exceptionally hardy and beautiful shrub is a firm favorite in many backyard borders but can easily get out of hand. Know when to cut back damaged stems and unruly growth and you will be rewarded with a healthy and shapely feature that’s smothered in vivid blooms.

Once you know when to prune rhododendrons, then it is also important that you know how to prune rhododendrons.

What time of year to prune Rhododendrons

Beautiful and hardy stalwarts of the border and rock garden, knowing when to prune rhododendrons is essential if you want to keep them in tip-top condition. 

These shrubs generally need little care and attention but occasionally you will need to thin and remove dead and damaged branches in which case this is best done after flowering as Dan Gilchrist of Swansons Nursery explains, ‘You can prune a rhododendron almost any time of year without harming it, but the best time is within a few weeks after it has finished blooming, to give it the maximum time to set flower buds for next year. Waiting too late is no disaster but could mean fewer blooms for the next year (or a few years if you are pruning it back hard).’

There may be a time when a mature rhododendron needs a complete overhaul. It could be that the overall shape has become leggy and unbalanced or that it has simply outgrown its space. Whatever the reason, this pruning job is not for the faint-hearted, and knowing when best to undertake it is key.

‘If your rhododendron needs to be significantly reduced in size using a saw, this should be done over winter when the plant is dormant, between January and March,’ says Kris Collins at Thompson and Morgan. ‘You may sacrifice a few flowers in the spring, but it gives the plant a whole season to regrow.’

Can I prune rhododendrons in winter?

The short answer is yes – but this is usually best for when the shrub needs completely rejuvenating. There are a few factors to bear in mind though, as Robert L Furniss of The American Rhododendron Society suggests, ‘Pruning of hardened wood can be done at any time except during periods of freezing weather.  Early spring generally is best because the new growth then has a full season in which to develop and mature.  Pruning immediately after the blooming period is standard practice.’

While hand pruners or secateurs may be useful for some light trimming back, Rhodo branches tend to be pretty hard and dense. Rather than struggling to make a cut and risk leaving the plant with broken or ragged branch ends that look unsightly and encourage disease to set in, opt for using loppers or a pruning saw for neat, clean cuts.