I often wonder how many gardeners remember their first few attempts at pruning plants that somehow ended up going awry! For me, it was a Smoke Bush, botanically named Cotinus coggygria. As a large shrub of 12-15’, it never grows uniformly and tends to sporadically throw long branches. The plant in question was slightly misshapen and I remember how I had to carefully place the step ladder so that I did not tumble into the neighboring kitchen window before making some judicious corrective cuts. Stepping back, it looked great, but within four weeks the plant had not only sent out new growth, but it was far more misshapen than before I began! Fortunately, 45 or so years of gardening have imparted some insights on how to work with this plant!
Cotinus is a member of the anacardiaceae, otherwise known as the Cashew or Sumac family. Cotinus coggygria is native from Southern Europe, through Asia and into Northern China, where it grows in poor and rocky soils in full sun. Similar to many plants, a number of botanists were involved with the development of its botanical name. The genus name of Cotinus was first penned by Michel Adanson (1727-1806), a French botanist and naturalist of Scottish descent. Cotinus may have come from the Greek Kótivoc or Kotinus, a reference to wild Olive Trees or from a shrub in the Apennine Mountains that was used to make a red dye that Pliny the Elder (23-79 AD) named Cotanus. The species epithet of coggygria was authored by Giovanni Antonio Scopoli (1723-1788), an Italian Physician and naturalist. In his 1772 edition of the book Flora Carniolica that describes plants of present day Slovenia, he properly named this plant which Carl Linnaeus (1707-1778) had previously name Rhus cotinus in 1753! The root of the epithet is from the Greek Kokkuyea or the Latin Coccygéa, perhaps a reference to the brilliant red fall color.
Although the roots of the name may be a bit challenging, Smoke Bush provides a multitude of interests for the garden and is certainly not a challenging plant to grow in the least! One of its most notable points of interest are the flowers that resemble puffs of smoke from a distance and are the inspiration for the common name (as seen in the image above and below right). The globe-shaped inflorescences are 6-12” long and roughly ½ as wide, but contain only a few five petalled flowers that are yellow-green in color and a mere 1/3” in diameter. The image above shows the formation of the resulting seed capsules. Fortunately, it is not the actual flowers that provide the floral drama, but the hairs or pubescence that appear on the pedicels and peduncles throughout the inflorescence. A pedicel is a short stalk that supports a flower while a peduncle is a stalk that supports a cluster of flowers or fruits! On the green foliage forms, the hairs range from green to deep pink, while on the purple leaved forms, the hairs are deep pink to purple, with the colors changing from June through July as the flowers age. Come autumn, the foliage assumes stunning bright red, yellow or orange fall colors before dropping for the winter.
As alluded to above, several cultivars exist that have deep velvety red or purple foliage during the growing season. ‘Black Velvet’, ‘Velvet Cloak’ and ‘Royal Purple’ are three of the older and more readily available forms and they actually do not need flowers in order to add impact to the garden. In fact, when they flower, the foliage assumes a less dramatic greenish-purple coloration. Since the late 1990’s, Rutgers Gardens has cut ‘Royal Purple’ back to a height of 12” each March – a process called stooling since the plant is cut back to the height of a stool leg (the image on the right shows the plant partially cut back). Since it sets flower buds on previous year’s stems, the floral impact is lost, but the foliage retains its deep purple coloration. With the stems shooting 8-10’ tall over the course of the season, it provides a great backdrop for flowering plants! The image above left is the same plant photographed in late May and shows the extent of growth in just a little over a month from bud break. If you are looking for a nice green selection, ‘Old Fashioned’ has very attractive bluish green foliage with pink flowers and pink, orange and red fall color. For more confined locations, consider ‘Young Lady’ (pictured above at left). It too has attractive green foliage, but it grows slowly to a more contained 5-6’ tall and is covered each year with attractive pink inflorescences. After 10 or so years it will benefit from a good pruning, as it too can become irregularly shaped.
If you are seeking plants native to North America, consider Cotinus obovatus or American Smokebush that grows in small populations throughout mountainous regions of Kentucky, Tennessee and Northern Alabama west to Oklahoma. In fact, some authorities consider the plant to now be rare and endangered. The plant was named in 1840 by Constantine Samuel Rafinesque-Schmaltz (1783-1840), a naturalist from Constantinople who lived in Kentucky. The species epithet refers to the obovate or egg shaped foliage that typically has a very attractive bluish-green coloration. The plant grows to 20-30’ tall with an attractive globe shaped crown. It is a much larger and tidier version of its more erratically growing cousin. It too prefers full sun and dry, well-drained soils. It can also tolerate nutrient poor soils, although growth is considerably slower under these less than ideal conditions. The fall colors are once again spectacular, ranging from yellow to red and purple. During 1978, Peter Dummer of Hillier Nurseries in England crossed Cotinus obovatus with Cotinus coggygria ‘Velvet Cloak’ and he named the best seedling ‘Grace’ in tribute to his wife. Grace is extremely vigorous, growing rapidly to 20’ tall with red foliage in spring changing to blue-green come summer. The flowers yield pink smoked inflorescences that are upwards of 14” long by 10” wide! Fall color is often a strong red (as seen above at right). If the plant becomes too large or unwieldly, they can be rejuvenated by cutting the plant back to 12” tall in late winter and new stems will rapidly arise, as seen at left. I have noticed this selection yielding more seedlings than other forms, all of which retain the attractive red colored foliage in spring. Cotinus obovatus and ‘Grace’ are hardy to zone 4, while Cotinus coggygria is cold hardy to zone 5. Another benefit to the foliage of all the species and selections of Cotinus is its resistance to deer browse.
Depending upon ones needs and the selection you pick, these plants can either be used as a small tree, as in the case of Cotinus obovatus, or as a screening shrub and a backdrop plant in mixed borders with the various selections of Cotinus coggygria. Its use is truly up to the needs or the imagination of the gardener. It is also clear that a gardener’s opinion of a plant cannot be firmly established on how well or poorly a plant responds to an initial attempt at pruning. I must admit I never thought I would appreciate this plant with sufficient zeal to actually write an article about it when I was 16. Fortunately, watching how others have designed and manipulated the plant has taught me that these smoky marvels make fantastic plants for the garden, something that I hope many gardeners will discover as well!