The cotinus, or smoke bush, is an important shrub for the garden because it has bright fall colors and early flower plumes. Shrub expert Andy McIndoe advises on how to grow them. Photographs by Richard Bloom.
Cotinus are big, hardy flowering shrubs that lose their leaves every year. They have pretty, round green, purple, or gold leaves and feathery flower plumes in the summer. The common name of smoke bush or smoke tree is inspired by the wispy character of its flowers. Most cotinus have excellent autumn colour.
The Battle of the Purple Smoke Bushes: Cotinus ‘Grace’ vs. ‘Royal Purple’
Smoke bushes also known as smoke trees, are prized ornamental shrubs for their vibrantly colored foliage and impressive plumes of smoky blooms. Two of the most popular purple-leaved varieties are Cotinus ‘Grace’ and Cotinus ‘Royal Purple’. But how do these two purple smoke bushes compare? In this article, we’ll examine the key differences between Grace and Royal Purple smoke trees to help you choose the best one for your landscape.
Foliage ColorBoth Grace and Royal Purple emerge with deep reddish-purple leaves in spring. However, Grace exhibits more color variation as the season progresses Its leaves take on blue and purple iridescent tones by summer. Royal Purple, on the other hand, maintains its rich purple hue throughout the growing season The foliage on mature Royal Purple plants tends to fade to a blue-green later in summer.
In autumn, Grace smoke bush dazzles with bright orange and black tiger-striped leaves. Royal Purple leaves turn more uniformly reddish-purple in fall. So for multi-colored foliage, Grace is the clear winner. But for deep purple leaves persisting into summer, Royal Purple excels.
Foliage SizeThe leaves of Grace smoke bush are significantly larger than those of Royal Purple. Grace leaves can reach 8 cm long, while Royal Purple leaves are typically only 3-5 cm. The giant leaves of Grace smoke bush are a result of its C. obovatus parentage. So if you’re looking to make a big foliage statement, Grace is the way to go.
Growth Habit
Mature size is another notable difference between these two varieties. Grace smoke bush grows larger, reaching 4.5-6 m tall and wide at maturity. It has an open, spreading habit with arching branches. Royal Purple matures at a more compact 3-4.5 m height and width. It has a rounded, multi-stemmed form.
Royal Purple is better suited to smaller residential landscapes, while Grace is an excellent choice for larger properties. Grace also works well as a screen or informal hedge due to its spreading shape.
Flowers
Both Grace and Royal Purple smoke bushes produce airy panicles of tiny flowers which give rise to their prized “smoke-like” seed heads. Grace displays deep pink blooms, while Royal Purple has softer pinkish-purple plumes. The flowers appear in early summer on both varieties.
The floral display tends to be more prolific on Grace since it blooms on both old and new wood. Pruning out old wood on Royal Purple can reduce flowering. So Grace wins for superior floral impact.
Hardiness and Care
No major differences exist between Grace and Royal Purple smoke bushes when it comes to hardiness and care. Both are hardy to zone 5 and thrive in full sun to part shade. They prefer well-drained soil and have moderate water requirements. Pruning is not required but can be done in late winter to early spring to maintain size and shape.
Grace and Royal Purple smoke bushes are relatively pest and disease resistant. Potential issues include leaf spot, powdery mildew, and leaf roller caterpillars. Proper site selection and cultural care will avoid most problems.
Availability
Royal Purple is the more common variety found at local nurseries. Cotinus ‘Grace’ is a newer introduction so may be harder to source. Both are available from reputable online nurseries that specialize in unique ornamental plants. ‘Grace’ tends to be more expensive due its large size and hybrid vigor.
Key Differences:
- Foliage colors – Grace shows more variation; Royal Purple is consistently deep purple
- Leaf size – Grace has very large leaves; Royal Purple has moderately sized leaves
- Mature size – Grace is significantly larger; Royal Purple is more compact
- Flowers – Grace has prolific deep pink blooms; Royal Purple has lighter pinkish-purple blooms
When to prune cotinus
Prune cotinus back hard in late winter or early spring. This will ensure an abundance of leaves and will keep the plant at a manageable size.
Where to grow cotinus
Cotinus are very hardy, tolerant of cold winters and some exposure to wind. They are easy to grow, thriving on most soils that are not too dry. Plants grow quickly and have good foliage when the soil is reasonably moist and fertile, but leaves often have a deeper color when the soil is dry. Smoke bushes thrive on clay and are a good choice for new-build gardens where space allows.
Cotinus can grow in some shade, but the best place for the leaves to look their best is in full sun and open space, especially for the purple-leafed types. In shade, these take on brown tints, while the golden-leaved forms turn lime-green. Too much shade results in few flowers and often more leggy growth.
Five brilliant Cotinus: how to grow smoke bush!
FAQ
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