Royal purple smoke bush, Cotinus coggygria, is a deciduous shrub that's also commonly known as smokebush, smoke tree, and purple smoke tree. Royal purple smoke bush is often used as a garden specimen thanks to its beautiful purple-pink plumes and the purple leaves on some cultivars. It grows best in USDA Hardiness Zones 4 to 9 and is highly drought tolerant.
Size and Shape of Purple Smoke Bush
The royal purple smoke bush grows in full sun to 12 to 15 feet tall and 12 to 15 feet wide.
The shape of each plant is irregular to rounded.
Foliage, Flowers, and Fruit of Royal Purple Smoke Bush
The leaves are oval and 1 1/2 to 3 1/2 inches long. The standard is a waxy green, although cultivars such as 'Royal Purple' and 'Velvet Cloak' have purple leaves. In the fall, leaves turn shades of red, purple, and orange.
The flowers are small and yellow-green, and they grow in groups that are 6 to 8 inches long. Most of them do not become fertilized, and the purple-pink plumes are the result of hairs on the infertile flowers. Purple smoke bush is dioecious, meaning it has "staminate and pistillate [male and female] flowers borne on different individuals."
The few resulting fruits are a half-inch drupe. A drupe is "a one-seeded indehiscent fruit having a hard bony endocarp, a fleshy mesocarp, and a thin exocarp that is flexible (as in the cherry) or dry and almost leathery (as in the almond)."
Design Tips for Royal Purple Smoke Bush
- Thanks to its beautiful colors, purple smoke bush can be used as a specimen shrub and for fall interest. The purple cultivars such as 'Redsmoke' are especially useful as a contrast in landscape design.
- Royal purple smoke bush is drought tolerant, so it's useful in xeriscaping, which is "a landscaping method developed especially for arid and semiarid climates that utilizes water-conserving techniques, such as the use of drought-tolerant plants, mulch, and efficient irrigation."
- Leaf colors in the fall are useful for design interest.
Growing Tips for Royal Purple Smoke Bush
- Royal purple smoke bush is able to grow in a wide variety of soils and ranges of pH.
- Propagation is by cuttings and seeds.
- Royal purple smoke bush has a fibrous root system and is easy to transplant.
Maintenance and Pruning
Royal purple smoke bush can be trained as a standard and used as a tree. Little pruning is needed otherwise.
Pests and Diseases of Royal Purple Smoke Bush
Obliquebanded leafroller, a native North American pest that feeds on a wide range of plants, can be a problem.
Royal purple smoke bush is very susceptible to Verticillium wilt, a browning of the leaves caused by the fungus Verticillium. It can also get leaf spot, a fungal condition prevalent in warmer weather, and scabs. If you are in the eastern United States, watch out for stem canker.