Butterfly bush is very cold hardy and can withstand light freezing temperatures. Even in cold regions, the plant is often killed to the ground but the roots can stay alive and the plant will re-sprout in spring when soil temperatures warm up. Severe and sustained freezes will kill the roots and plant in United States Department of Agriculture zone 4 and below. If you are concerned about butterfly bush winter kill in your region, take some tips on how to save the plant. There are several steps to preparing butterfly bushes for winter and saving these colorful plants.
Butterfly Bush Winter Kill
Even in a temperate zone, there are chores to do to help plants withstand winter storms and weather. Butterfly bush winter protection in warmer climates usually just amounts to some extra mulch around the root zone. We’ve been asked, “do I prune my butterfly bush for winter and what other preparation should I take?” The extent of overwintering preparation depends upon the severity of the weather the plant will experience.
Buddleia lose their leaves in fall in most areas. This is a common occurrence and may make it appear the plant is dead but new leaves will arrive in spring. In zones 4 to 6, the tops of the plant may die back and no new growth will come from this area, but not to worry.
In spring, new growth will rejuvenate from the base of the plant. Prune off the dead stems to retain an attractive appearance in late winter to early spring. Container grown plants are at the most risk of damage from winter chill. Move potted butterfly bush indoors or to a sheltered area to protect the roots from the cold. Alternately, dig a deep hole and put the plant, pot and all, into the soil. Unearth it when soil temperatures warm up in spring.
Pruning butterfly bushes annually actually enhances the flower display. Buddleia produces blooms from new growth, so pruning needs to be done before new growth appears in spring. In areas with ice storms and severe weather that can break plant material and cause damage to the structure, butterfly bush can be severely pruned and it will not adversely affect the flower display.
Removing errant stems and growth will help prevent more acute damage from winter weather and is a sensible way of preparing butterfly bushes for winter in any region. Place a 3- to 4-inch layer of mulch around the root zone as further butterfly bush winter protection. It will act as a blanket and keep roots from freezing.
How to Overwinter a Butterfly Bush Indoors
It is common to move tender plants inside to protect them from cold weather. Buddleia grown in cold zones should be dug up and placed in potting soil in containers. Do this in late summer to early fall so the plant has a chance to adjust to its new situation.
Water the plant regularly but slowly diminish the amount of moisture you give the plant a couple weeks before the date of your first frost. This will allow the plant to experience dormancy, a period when the plant is not actively growing and is, therefore, not as susceptible to shock and site changes.
Move the container to a location that is frost free but cool. Continue to water sparingly throughout winter. Gradually reintroduce the plant to the outdoors when soil temperatures warm up. Replant the butterfly bush in prepared soil in the ground after all danger of frost has passed.