The cotinus is an attractive, small tree suited for dry, rocky locations. It is a slow-growing tree, and can reach a height of 20 feet. The leaves are an attractive green, yellow or purple, depending on the variety. It is the fine, wispy blossoms that give cotinus the name "smoke tree" or smoke bush. Pruning a cotinus is a matter of forming the plant into a shrub or tree form, depending on the landscape plan. Like many other spring-flowering shrubs and trees, the smoke tree is normally pruned in early summer after it is finished blooming.
Select the branches to prune. If the landscape plan requires a shrub form, prune the smoke tree back to nearly ground level to encourage multiple stems to develop. Repeat this severe pruning the first two years after planting, then allow the stems to grow into a shrub. Trim the branches to shape after blooming.
Select one to three main trunks to train into a tree form. Cut other stems all the way to the ground.
Remove the lower branches to expose the smoke tree's trunk. Allow the upper branches to grow into a loose, open form, pruning only to remove low-hanging, broken or diseased branches.
Cut just above buds when trimming branches. Do not leave an unsightly stub that will die back to the bud.
Remove branches showing signs of Verticillium wilt. The entire branch will suddenly wilt and die; completely remove the infected branch and put it in the trash. Mix a 10 per cent bleach and water solution in a bucket. Sterilise the pruning tools by soaking them for at least 30 seconds and allow them to completely dry before reusing.
Prune in early summer after the smoke tree has bloomed. If the tree is infected with Verticillium wilt, rake up all mulch and leaves and place them in the trash. Replace with fresh mulch. Water and fertilise the tree.
Wear gloves, safety glasses, long sleeves and long trousers when pruning. Some varieties of smoke trees have thorns. Do not prune smoke trees in winter or early spring, as you will cut off all the flower buds.