St. John’s Wort is a hardy deciduous shrub that survives winter conditions in zones 4-9. In the colder zones, the shrub is fully deciduous, losing all of its leaves and going into complete dormancy for the winter. In the warmest growing zones, St. John’s Wort will behave more like a semi- or evergreen shrub, retaining foliage through the winter and only losing it as the new growth emerges in the spring.
Protecting St. John’s Wort in Winter
The lovely berries that St. John’s Wort produces in late summer do not need to be removed for the winter. In all of the growing zones, wildlife will appreciate the added nutrition through the winter months. St. John’s Wort will tolerate periods of snow cover and is easily pruned back in the spring after all danger of frost has passed. In the warmer zones that have excessive rain during the winter, drainage is the main issue to pay attention to. Seasonal ponding in garden beds or pots that sit in standing water will quickly rot the roots and cause severe damage and/or death to St. John’s Wort.
Cutting Back St. John’s Wort For Winter
St. John’s Wort does not need cutting back in the fall. Leaving the berry stems will provide food for garden wildlife and also help to insulate the growing crown. Any pruning should be done in the early spring as new growth is emerging. Any branches with winter damage can be cut back to the main stem. Spring is also the time to do any hard pruning to rejuvenate St. John’s Wort.
St. John’s Wort Winter Care in Pots
St. John's Wort is a great container plant that survives the winter just fine. Make sure the container you are using has adequate drainage before the first freeze. Plants do not like to sit in cold, waterlogged soil. The roots of container-grown plants are less insulated than those of plants in the ground. A good rule of thumb for containers is to treat the plant like you are growing it in one zone colder than yours.
Zone 4 pots should be treated like zone 3, etc. If you live in the lower end of its growing range, you can move containers to an unheated garage until early spring. Wrapping the pots in layers of burlap or horticultural fabric can also provide added insulation for the roots.
Watering St. John’s Wort in Winter
You can stop watering shrubs after the ground begins to freeze for both those planted in the ground and in containers. The plants will have gone dormant and are not actively taking up moisture. Make sure that the garden bed and pots are not waterlogged through the winter. The roots should not be left to sit in water long enough to rot. Cold, wet soil is the most common reason for losing a shrub over the winter. Pots that have been moved to a sheltered location will not require extra watering either. Watering can resume after the last frost in late winter or spring.
Growing St. John’s Wort Indoors
St. John’s Wort can be grown indoors as long as it has adequate light and is not placed near a heat source like a furnace vent or radiator. Keep watering to a minimum while it is indoors. Letting the pot dry out between waterings will prolong the berry display and help to protect the roots from rotting.
Steps To Care For St. John’s Wort in Winter
St. John’s Wort is a shrub that can tolerate a fairly wide range of winter conditions and will regrow year after year with minimal protection.
Step 1 - Wait until spring to prune the previous season’s growth, which will help to insulate the growing crown in winter
Step 2 - Move pots if they are in standing water or in danger of being washed out by downspouts or roof lines
Step 3 - Move the container into an unheated garage if you garden in zones 4 or 5
Step 4 - Stop supplemental watering at the first freeze of the season and resume watering after the last freeze in spring.
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