St. John’s Wort is a small shrub that is sometimes referred to as a woody perennial. The flowers and berries form on new growth that starts out green and turns woody by the end of the summer. Many cultivars of St. John's Wort are grown specifically for both their flowers and the ensuing sprays of berries. Pruning at the right time of the year is important to encourage bushy, dense growth while preserving the most ornamental traits of St. John’s Wort.
When to Prune St. John’s Wort
Pruning St. John’s Wort only needs to be done one time a year. Early spring is the time to remove any damage from the winter and all of the old growth from the previous season. Cutting St. John’s Wort back to fresh wood will help to keep it compact and flowering vigorously. Spring is also the time to do any rejuvenation pruning. Since this shrub blooms on the current season's growth, spring pruning will not reduce flowers or berries.
Do not deadhead St. John’s Wort if you want the berries to form. However, if you would like to prevent self-seeding, remove all the spent flowers before they set seed. The berries are seed capsules that form when the flowers are left in place. Once the berries form, the whole plant will start to prepare for dormancy.
Why Prune St. John’s Wort
Pruning in the spring will encourage compact new growth on St. John’s Wort. This compact growth will support more flowering and berry production. Cutting out all of the winter-damaged material will keep the shrubs healthy and more resistant to pests and diseases. Some cultivars of St. John’s Wort are vulnerable to mildew and fungal diseases. If you notice any diseased foliage, prune out the affected branches as soon as possible to keep the disease from spreading through the plant or to neighboring plants.
How to Prune St. John’s Wort
Step 1 - Early spring pruning
Cut out all diseased, dying, damaged, or diagonal growth back to the main stem. Also, cut back all of the dead growth from the previous year.
Step 2 - Rejuvenation pruning
Early in the spring, cut the whole shrub back to fresh woody growth. This may take the shrub down to within 6 or 8 inches of the ground. The shrub will put out new growth quickly without losing a season of blooms or berries.
Step 3 - Disease clean-up during the summer
If diseases do attack the shrub, cut out all affected parts as soon as possible. Removing affected branches will control the spread of disease to other plants.
St. John’s Wort Pruning Tips
- Prune in the spring to clean up any winter damage
- St. John’s Wort blooms on new growth
- Rejuvenation pruning needs to be done early in the growing season
- Diseased branches should be removed as needed
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Author Robbin Small - Published 8-15-2022