Fall pruning isn’t for every plant
When summer is over and cold weather is on its way, we often take to the garden with our pruning sheers and loppers and get to cleaning up before the snow falls. But not everything needs to be pruned in the fall. In fact, many plants do better if pruned in spring, before or right around the time new growth starts appearing.
One of these plants that sticks out in my mind is Buddleia davidii, also known as butterfly bush. This plant is not to be confused with the common orange-flowering butterfly weed, Asclepias tuberosa. Asclepias is closely related to milkweed and is a great addition to a wildlife garden, but many people aren’t attracted to the bright orange flowers and prefer something a bit more subtle, like the purple and lavender flowering butterfly bush. (I’ve said it before and I’ll say it again, common names are confusing).
Butterfly bush is probably one of the fastest growing flowering plants I’ve had in my garden. Each spring, just as the new growth starts showing at the base of the trunk, I take my loppers and cut down everything left over from last year to about six inches from the ground.
If I lived in a warmer climate, this wouldn’t be the case. Buddleia is a deciduous shrub in warmer areas that, although it drops its leaves for winter, branches and stems will produce new growth the following season and plenty of blooms. That isn’t the case here in the cold north. Since Buddleia only flowers on new growth, that thick trunk and all those branches and stems won’t produce anything new. Once those bare branches are pruned away, the new growth coming up from the base will quickly grow to about six to eight feet tall and will be covered in those long, panicles of flowers that attract butterflies, hummingbirds and even those enormous hummingbird moths, which are actually adult hornworms.
So why wait until spring to prune this plant, since it drops its leaves in the fall? The reason is because Buddleia stems are hollow. Water seeping down into the hollow stems and then freezing over the winter will cause the woody trunk to split and that can cause root damage and create a portal for disease.
Another plant to wait until spring to prune is Black-eyed Susan, Rudbeckia fulgida. Although this plant isn’t particularly attractive once the flowers have dropped and the seedpods sit atop gray, dead-looking stems, the birds will be happy. If you can stand the messy look of black-eyed Susan over winter, they are great for feeding the birds when there isn’t an abundance of seeds anywhere else.
Still other plants, such as astilbe, dianthus (Pinks), and balloon flower (Platycodon grandiflorus), have other reasons for not pruning until spring. These plants retain their old foliage over winter, although it is wilted and wet by spring and new growth will soon follow once the time is right. Cutting the old growth away in the fall makes it difficult to find the plant in early spring. The old leaves and stems can act as markers so we know where to start looking for new growth. Once the new growth appears, we clean up the old stuff and simply wait for the season to begin.
Gardening, like life in general, takes a bit of patience.