I’ve never seen the tree form of Cotinus coggygria (smokebush/smoketree) for sale at a nursery. Because I wanted a smoketree to complement my cream-colored house, I bought a velvet cloak purple smokebush (#7 container size) to see if I could prune it into a tree. After buying it, I planted it and left it alone for the first two years.
Little did the smokebush suspect that I planned to transform it into a single- or multi-stemmed tree that would reach 10 to 15 feet at maturity.
With its gorgeous, translucent, spoon-shaped leaves and fluffy seedheads, a smoketree is a real standout in the garden. As a bonus, the velvet cloak cultivar displays stunning reddish-purple foliage each fall.
I’ve read that if you want to prune a smokebush into a smoketree, you should begin pruning when the shrub is young. Smokebushes are notorious for suckering, and once a gazillion suckers have taken hold, pruning the shrub into a tree is extremely difficult.
So early this spring, I selected a leader (central branch) from the smokebush’s branches and pruned all of the remaining branches down to the ground and even a little below ground when possible. I then staked the leader into an upright position, using a length of bicycle inner tube and a steel T-post.
In the process, I noticed another branch about a foot away that also had leadership potential. So to hedge my bets, I staked that one, too.
So far, the leaders look promising. One is about 1 inch in diameter; the other is about 5/8 inch. Since staking them three months ago, I have seen them grow in height from about three feet to nearly six feet. Smokebushes grow very rapidly at first before slowing down.
Naturally, new suckers have grown at the base of each leader. But every couple of weeks, I just go out and prune them away.
Some say that smokebushes can be difficult to establish in Colorado and that they die back to the ground during their first few years. I didn’t find that to be the case. My smokebush happily took to my front yard with no dieback during two winters.
I’ll continue to prune away the suckers and, as the leaders grow taller, prune away some of the lower branches as well. Watch for updates to this process.
4/11/2015 update: The main leader continued to grow nicely, so I ended up cutting down the smaller 5/8″ leader. Last month, I sold my house and moved, so sadly, a builder will likely cut down the tree when he demolishes the house. But at least I now know that it’s relatively easy to prune a smokebush into a smoketree. Just be aware, however, that the trunk will be somewhat irregular, but that may well be part of the tree’s charm.