Re: How to prune smoke bush into tree form?
You can either leave the three main stems and remove any smaller, or if you prefer a tree with a single trunk, you will need to choose one of the stems to be the main trunk and cut everything else. As the shrub grows taller, begin to remove any lower horizontal branches. Cotinus should be pruned in early spring to avoid removing flower buds. Here is some general info on Cotinus. For more detailed info on pruning for tree form, read the Shaping Tree-Form Shrubs section of this fact sheet from Clemson’s extension website.