Pruning made easy: berberis 'Rose Glow'

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This prickly deciduous shrub needs thinning and shaping. Jon Brocklebank of Barnsdale Gardens explains what to do

THESE GOOD VALUE shrubs provide leaf colour, flowers and berries during the year. But to flower well, all berberis need annual pruning, removing a proportion of the old wood to create more space for new, flower-bearing shoots.

Deciduous cultivars such as ‘Rose Glow’ shown here, with its reddish-purple stems and marbled leaves, can be pruned while it’s dormant in winter to promote the growth of vigorous new stems and foliage next spring. (Note that pruning now will reduce the flower display Mar-Apr; prune after flowering if you don’t want to cut off any developing buds.)

The aim is to thin out and remove older stems, pruning them right down low, but don’t remove them all. Although you can chop the whole plant down low to stimulate loads of new growth with good foliage, for a better balance of young and old wood, it’s best to use the 1-in-5 rule – thinning out one in every five branches. This plant is about 25 years old; the brighter, reddish-brown stems are this year’s growth so it’s fairly easy to tell them from the older stems.

Read the plant before you start – look for tightly congested areas. Identify stems that are dead, diseased or damaged and remove these first. Shorten them to a new sideshoot or remove to the base.

These shrubs have a naturally crowded, arching habit and here many of the stems are carrying a lot of old growth so the really low branches will get heavy at the ends. I don’t want them all to stand upright, but I may shorten them to a suitable bud or upright new shoot so the silhouette isn’t so lax. 

Pick through the congested areas steadily, taking out stems that offend – such as where old wood is getting a bit long. This thinning process will gradually open the plant up, improving overall shape.

If you’re renovating a really overgrown or neglected berberis, cut the entire shrub down in spring to within 30cm (12in) of ground level so it can regenerate from the base. It will put on lots of good leaf but you’ll lose the flowers and berries in the coming year, as these only grow on older wood.

As with any pruning, tread carefully. Take stems out, look at the plant and consider what’s going to be left behind – then take more off if required!

TAME YOUR BERBERIS STEP BY STEP

1. READ THE PLANT Look for congested areas and identify dead, diseased and damaged stems. Select one-in-five of the older stems to remove so you don’t prune too hard. Flowers and berries form on older wood.

2. THIN OUT CONGESTION Use the one-in-five rule to remove just a few of the older stems. This will rejuvenate the plant and create a more open shape.

3. CUT TO A STRONG PAIR OF BUDS Cut out crossing stems and a fifth of the older stems to allow light in and make room for new shoots. Cut back to a strong pair of buds, to encourage new growth. 

4. REMOVE CROSSING STEMS Shorten one of the crossing stems to a new sideshoot or remove it to the base. Choose between stems by prioritising the younger one or the one in a better overall position.

5. REMOVE LAX BRANCHES Although the shrub has an arching habit, removing the lower stems and shortening the really long ones helps create a slightly more upright silhouette.

6. KNOW WHEN TO STOP After each cut, consider the effect that your pruning choices are making on the overall silhouette of the plant. Plants do respond well to strong pruning so don’t worry too much if you ‘overdo’ it.