How to prune hypericum

Hypericum is a large group of plants that includes everything from annuals and perennials to shrubs, trees and those suitable for ground cover. “St John’s Wort” is often used to refer to any species of the genus hypericum, while the more specific Hypericum perforatum is called “common St John’s Wort”, or “perforate St John’s wort” to differentiate it. Here’s how to prune your hypericum to encourage thick bushy growth and a beautifully maintained shape. 

When to prune hypericum

This low-maintenance shrub requires very little pruning
Image: Hypericum 'Hidcote' from Thompson & Morgan

Two of the most commonly grown members of the hypericum family are H. x hidcoteense, a small semi-evergreen shrub, and H. calycinum, a low-growing shrub that is also known as ‘Rose of Sharon’. Both produce bright yellow flowers that appear in late summer.

Hypericum doesn’t need to be pruned regularly, although it’s always advisable to remove any dead wood and give the plant a light shape each spring, to keep it looking good. Use a pair of sharp, clean secateurs or shears.

How to prune hypericum plants

Trim with shears each spring to create an attractive, low-growing hedge
Image: Hypericum Calycinum 'Rose of Sharon' from Thompson & Morgan

H. calycinum (Rose of Sharon) grows vigorously and it should be cut back annually in spring to encourage fresh growth and to keep it contained. It can be trimmed into an attractive, low hedge that flowers from July to October, even in areas of deep shade. 

Hypericum x hidcoteense is a shrub that can be reduced in size by cutting back in the spring. Remove any weak or thin growth and then trim back the rest to a strong shoot. This will help to keep the shrub compact.

It’s also a good idea to completely remove some of the old wood to open up the shrub and give it a better shape.

If an old shrub needs rejuvenating, cut it back hard to about 30cm in spring. It should then put on fresh growth.

Hypericum are low maintenance plants that require very little regular pruning other than what is required to keep it in shape. Should they get out of hand, a hard prune in spring is unlikely to do them any harm.

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Written by: Mandy Bradshaw, the Chatty Gardener