The smoke bush or Cotinus coggygria is a large, deciduous, broad-leaved shrub that requires full sun to partial shade. It can reach a height of 15 ft. and a spread of 15 ft. The name smoke bush is derived from the fine-filament clusters or smoky plumes that appear on the bush during the summer. It is often used as a specimen planting or a shrub border in landscape design. The shrub should be pruned to remove diseased, dead, or broken branches; to control its size and shape within your landscape design; and to develop a dense shrub with numerous stems. You can prune these shrubs by heading or thinning.
Prune away any diseased, dead, or broken branches as soon as possible--any time of year--to ensure the health and integrity of the smoke bush. Where you cut depends on where the branch is. Diseased branches should be entirely cut out at the base or trunk of the shrub. But you can prune broken and dead branches at the base of the shrub or where the broken or dead wood is. Consider the overall appearance of the shrub when deciding where to prune. If you don't cut the entire branch, prune about 1/4 in. before a bud.
Heading controls the size of the shrub so it fits the landscape design. Heading also shapes the shrub by cutting back branches. Cut the branch back to 1/4 in. before a healthy bud. This should be done after the smoke bush has flowered in the spring.
Thinning is done in combination with heading. This also controls the shrub to fit the landscape design, and shapes it by cutting out certain branches down to the ground for a smoke bush with numerous stems. The smoke bush can also be shaped like a small tree with a single stem or trunk; certain branches are back to the trunk or main stem. Thinning allows more sunlight into the flowering bush and increases air circulation. Thinning and heading shapes and sizes the bush and should be done in spring after the smoke bush has flowered.
Form a dense bush with numerous stems by radically pruning the smoke bush to 2 to 3 in. from the ground. Do this in late fall or early spring. This severe pruning should be done for two years after planting. The bush will not produce flowers during this radical pruning, but you will enjoy the beautiful purple foliage--some cultivars have green or yellow leaves--during the summer growing season.