Smoke Bush

Asked April 20, 2020, 8:36 AM EDT

Hello, I am a novice gardener and would like some help with a smoke bush. I have been doing some research and it turns out that I have been pruning incorrectly- I have a lot of water sprouts. I am thinking about cutting it way back so that it can start again but I am not sure how to do that exactly. My smoke bush has multiple main branches. How far down can I cut back to? When would be the best time to do this?

Also, I noticed white circles on the branches. Can you tell me what that is and how to I fix it? Please see enclosed photos.

Thank you so much!

Macomb County Michigan

1 Response

I am adding the information below which came to Ask an Expert with the same question as you.
Timing is important for pruning a smoke tree. If you prune it at the wrong time,
the tree reacts to the stress of pruning by growing wildly and haphazardly.
Here is some advice.
When to Prune a Smoke Tree or Bush
Trimming smoke trees can be done in late winter or very early spring. As a general rule, pruning smoke trees for shape is done in very early spring when the plant is still mostly dormant and the process will create less stress. Summer flowering shrubs such as smoke tree need to be pruned before flower buds have shown.
The rule for pruning deciduous flowering plants is that if it flowers after June 1, like the smoke bush, you need to prune in early spring. You can shape it at this point and keep the plant below a certain height. General pruning will include removing old wood, diseased or broken plant material and managing any suckers and water spouts. Any crossed branches need to be removed to prevent crowding and rubbing.

As you are seeing with your shrub, if you prune at the top of the shrub (rather than all over to shape and take out larger branches), the shrub will be encouraged to grow from the base. Looking at the shape of your shrub, I would suggest that you take some time now to re-shape it by cutting back the larger limbs for a gradual renewal pruning. In other words, don't cut all branches down - just the larger ones. Then lightly prune back the remaining smaller branches to reshape the shrub. Below are a couple of articles about the various purposes for pruning as well as techniques.
https://www.canr.msu.edu/news/spring_shape_up_tidying_up_your_plants
https://www.canr.msu.edu/news/tips_on_tree_and_shrub_pruning

I'm not sure if you are interested, but on May 5th there is an online pruning workshop being offered by an MSUE educator, Rebecca Finneran. The cost is $40 and you will be able to see pruning techniques close up and ask questions of the instructor. The link for the registration site is: https://events.anr.msu.edu/2020May8PruningWorkshop/

As for the white spots, they look like lichen to me and are not harmful to the tree. Hope that helps!