Tips On St. John’s Wort Pruning: When To Cut Back St. John’s Wort

Close up of a St. John's Wort flower with yellow petals and red stamens
(Image credit: Stacy Matte)

That bushy plant in your garden bearing yellow flowers summer through fall, the one known as St. John’s wort (Hypericum "Hidcote") may be considered low maintenance, but it flowers more prolifically if you give it an annual haircut. Read on to learn how and when to cut back St. John’s wort.

St. John’s Wort Pruning

St. John’s wort is an undemanding shrub that grows in U.S. Department of Agriculture plant hardiness zones 5 through 9. If your shrub has fewer and fewer flowers every year, you may want to start pruning St. John’s wort.

These are delightful plants to have in your garden: bright and colorful and easy care. However, annual pruning is necessary to keep the St. John’s wort nicely shaped and full of summer flowers. It also helps keep the plant in check overall, as it can be prone to getting out of control in some places.

When to Cut Back St. John’s Wort

St. John’s wort flowers on new growth. This means that all the blossoms you see in summer bud and bloom on the new wood the plant grows in spring. You must take this timing into account as you decide when to cut back St. John’s wort. You don’t want to reduce summer flowers by cutting off the new growth that will produce them.

In fact, early spring is the time to do St. John’s wort pruning. Cutting back St. John’s wort shrub just before the new growth begins is ideal.

How to Prune a St. John’s Wort Shrub

Before you start cutting back St. John's wort, be sure your shears are clean and sharp. Sterilize them, if necessary, in a mixture of bleach and water.

If you are wondering how to prune a St. John’s wort shrub, here are some tips:

  • Plan on pruning off about one-third of the total height of the shrub in mid or late March.
  • Pruning St. John’s wort involves reducing all branch tips and selectively removing some branches to thin the plant.
  • You should remove any branches that are dead, damaged, or crossing. Remove others from crowded areas.

Cutting back St. John’s wort increases flowering because every place you make a cut will branch into two stems. Each of those stem tips will develop a separate blossom cluster.

Even if your shrub hasn’t flowered for a long time or appears beyond repair, give it a chance. You can prune St. John's wort very severely – almost all the way to the ground – to rejuvenate it.

Teo Spengler

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.