Summersweet (Clethra alnifolia) is a low-maintenance shrub that doesn’t necessarily need to be pruned. However, this shrub can benefit from early spring pruning, especially to remove any damage caused during the winter. Summersweet blooms on new wood, meaning that some of the branches and trunks from the previous season can be trimmed back in the early spring without the risk of preventing flowers from emerging in the late summer.
To limit the size of Summersweet, suckers growing around the plant from the roots can be cut back as well. Throughout the year, dead and damaged parts of the plant can be removed to keep Summersweet looking happy and healthy.
When to Prune Summersweet
Summersweet is best pruned in the early spring when the plant is still dormant or just starting to wake up. By pruning early, you are encouraging the plant to focus on new growth, which will provide more vigorous blooms in the late summer. At this time, it is a good idea to remove any dead lower or inner branches to create better airflow. Any leftover fruiting capsules or seeds can be removed as well. Pruning Summersweet back a couple inches a year will prevent it from looking unruly or overgrown.
At other times of the year and once Summersweet has begun producing new leaves and branches, minimal pruning is necessary. Because Summersweet will bloom on new wood, you will want to avoid making any cuts that may reduce late-summer blooms. If any branches are broken or damaged, they can be removed. Once Summersweet has finished blooming in the fall, the spent flowers can be removed, though it is likely too late in the season to expect any further blooms. Some choose to leave spent flowers, however, as their seeds and fruit can add some winter interest.
Why Prune Summersweet
While pruning Summersweet is not necessary, especially if willowy or native looking is the garden aesthetic you are going for, giving it a light trim in the early spring may set the plant up for a showier bloom later in the year. If Summersweet is being used as a hedge or if a more sculpted look is desired, spring is the best time to do your heavy pruning.
Summersweet can grow quite large and wild looking, and pruning and removing suckers can mitigate this. In addition, trimming out damaged or crowded branches can improve air flow and reduce the number of places pests can hide.
How to Prune Summersweet
Step 1 - Wait until spring
While the spent blooms can be removed in the fall, you will want to wait to tackle any major pruning projects until the early spring when Summersweet is still dormant. Pruning at this time will stimulate new growth and give you a chance to remove any winter damage.
Step 2 - Prune to shape
This early spring prune is your chance to trim Summersweet into the shape and size you would like. Remove up to ⅓ of the plant with sharp, sterile pruners or loppers and trim any dead or damaged branches down to their source. Removing more than ⅓ of the plant may stunt its growth, so cut accordingly. If you are growing Summersweet as a hedge, avoid trimming the sides located next to other Summersweet plants.
Step 3 - Remove suckers
Summersweet spreads underground through the production of suckers. These suckers can cause Summersweet to look unruly, and their removal will prevent them from spreading into other parts of your garden. With a sharp spade, dig down around the sucker, breaking its connection with the mother plant. If desired, suckers can be moved to another location as a form of propagation.
Step 4 - Removing dead branches
Dead or damaged branches can be removed at any time during the year. These unhealthy parts of the plant provide a place for bugs and disease to reside, so it is best to remove them even outside of springtime.
Summersweet Pruning Tips
- Prune in the early spring when Summersweet is still dormant
- Cut to shape and size desired
- Remove suckers from the ground as needed
- Early spring pruning will improve late summer blooming
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