Smoke bush, Cotinus coggygria, is a deciduous shrub that's also commonly known as royal purple smoke bush, smokebush, smoke tree, and purple smoke tree. Smoke bush is often used as a garden specimen thanks to its beautiful purple-pink smokey plumes and the purple leaves found on some cultivars. It grows best in USDA Hardiness Zones 4 to 9 and is highly drought-tolerant.
Smoke bush has an upright, multi-stemmed habit. The leaves are waxy green except for those cultivars with purple leaves, and are 1 1/2 to 3 inches long, ovate in shape. The leaves turn yellow, orange, or purplish red in fall, depending on variety. The name "smoke bush" derives from billowy hairs that are attached to the flower clusters and which remain in place through the summer, turning a smoky pink to purplish pink as the weeks progress. Purple smoke bush is dioecious, meaning it has "staminate and pistillate (male and female) flowers borne on different individuals. Smoke bush is often used as an individual specimen plant, and in larger landscapes, it can be massed or planted as an informal screening hedge. Smoke bush is drought-tolerant, so it's useful in xeriscaping and other applications where water conservation is important.
- Botanical Name: Cotinus coggygria
- Common Names: smoke bush, purple smoke bush, smoke tree, smoketree, European smoketree, Eurasian smoketree, Venice sumach, dyer's sumach
- Plant Type: deciduous shrub
- Mature Size: 10 to 15 feet high, similar spread
- Sun Exposure: Full sun
- Soil Type: prefers infertile loam, but tolerates all soils except wet, poorly drained soils
- Soil pH: tolerates both acidic and alkaline soils
- Bloom Time: late spring to mid-summer
- Flower Color: yellow
- Hardiness Zones: 4 to 9 (USDA)
- Native Area: southern Europe to central China
How to Grow Smoke Bush
Smoke bush should be planted in full sun, but it does well in almost any soil type and most any pH level. The ideal circumstance is slightly sandy loam, but they also do well in rocky soils. The only soils not well suited are dense, soggy wet conditions. In zone 4, plant them in slightly sheltered locations to protect from winter winds. When grouping plants, they should be spaced 10 to 15 feet apart.
Young plants should be watered deeply and regularly, but once established, smoke bush has good resistance to drought. Mulch the base of the shrubs with wood chips or bark mulch to keep weeds away and soil moist.
The only mandatory pruning is to remove dead or damaged wood, but the shrubs will tolerate hard pruning to shape them or rejuvenate them.
Smoke bush should be planted in full sun. In part shade conditions, foliage will be sparse, requiring regular pruning to keep the plants dense.
Smoke bush does well in nearly all soil conditions provides the soil is well drained. It does not tolerate damp, soggy soils.
Once established, smoke bush has good tolerance for dry conditions. When getting established, the shrubs require regular watering, but mature plants thrive nicely if watered moderately every 10 days during the active growing season.
Temperature and Humidity
Smoke bush does best in moderate temperatures and in average to dry humidity levels. In moist, very warm climates, fungal diseases are often a problem. In colder climates, winter winds can damage the plants, so they should be planted in sheltered conditions in these regions.
Smoke bush does not require much in the way of feeding. Fertilize them in spring with a layer of compost. An annual application of organic plant food may be called for if the shrubs are not growing vigorously. The main needs are for nitrogen to fuel the growth of foliage.
Propagating Smoke Bush
Propagation of smoke bush is by cuttings and seeds. A leafy stem stripped of its lower leaves and embedded in a growing medium will easily root itself. Seeds should be soaked in water for 24 hours, dried, then planted about 1/2 inch deep in sandy soil.
Smoke bush has a nicely contained fibrous root system and is easy to transplant. Start by root-pruning the shrub several months before you plan to move it by digging a 12-inch to 24-inch circle, 14 inches deep, around the plant's base. At transplant time, dig down around the tree 12 to 14 inches, then lever the root ball out of the ground and move the shrub to its new location.
Varieties of Smoke Bush
- 'Daydream' is a good green-leaved cultivar with dense, creamy blooms. It is a somewhat smaller plant, growing to a maximum of 10 feet wide and tall.
- 'Nordine' is a very hardy purple-leaved variety. It has yellow-orange fall foliage.
- 'Royal Purple' is a common purple-leaved form with dark foliage and purple-red "smoke."
- Velvet Cloak' is another dark purple-leaved form; it has dramatic orange-red fall color.
Smoke bush is a large shrub, and it can work well as a background screen with early-blooming shrubs such as lilac, viburnum, or spirea in the foreground. Hydrangeas, Rudbeckia (black-eyed Susans), and Achillea (yarrow) also pair well with smoke bush.
Pruning needs are minimal with smoke bush. You can prune anytime to remove damaged branches, but spring is the best time to prune in order to shape the shrub or rejuvenate it. If you wish to avoid the messy flowers, prune heavily in spring to remove the flowering wood.
If you wish to encourage a tree-like growth habit, prune away all but one central leader stem, and keep pruning away any stems that reappear. A bushier shrub can be obtained by cutting all stems down to ground level in late winter for the first two or three years.
Obliquebanded leafroller, a native North American pest that feeds on a wide range of plants, can be a problem with smoke bush.
If soils are not well drained, smoke bush is very susceptible to verticillium wilt—a browning of the leaves caused by the fungus Verticillium. It can also get scabs and leaf spot, a fungal condition prevalent in warmer weather. If you live in the eastern United States, watch out for stem canker.