A Colorful North American Native–American Smoketree
Cotinus obovatus, American Smoketree, is sometimes inaccurately described as having large, showy pink flowers. In fact, Smoketree gets its common name from the billowy hairs attached to elongated stalks on the spent flower clusters. These hairs turn a smoky-pink to purplish-pink in summer, covering the tree with fluffy, hazy, smoke-like puffs. Berries occur on pinkish stems and then dry to small dark seeds. Spring leaves are silky pink, turning bluish-to-dark green. Fall leaves are magnificently colorful, turning vibrant shades of red, orange, yellow and purple. C. obovatus is attributed with having one of the best fall color displays of any of our North American naive trees. The color can last up to a month. Its gnarled limb structure and interesting fish-scaled bark pattern add to winter interest, giving it a true four-season display. Extract from its deep orange-yellow heartwood was used to make yellow and orange dyes, especially around the time of the Civil War. The tree was harvested for dye almost to the point of elimination.
C. obovatus is an upright, small tree or multi-trunked shrub, depending on how it’s pruned. It has a mature height of 15-30 ft. and should survive for at least 60 years. It is described as hardy and adaptable to many adverse soil conditions. It grows best in full sun and alkaline soil but can tolerate partial shade, slightly acidic soil, and compacted soil. It does not respond well to overly rich soil, over-watering, or over-fertilizing. It is drought tolerant, disease-resistant, and is highly tolerant of urban pollution which allows it to thrive in inner city environments.
NATIVE U.S. AREAS
This North American native tree is found in the rocky, mountain soils of northern Alabama, Arkansas, Georgia, Kentucky, Missouri, Oklahoma, Tennessee and some parts of central Texas. In cultivation, the species has proven to be cold hardy in the north and thrives in a far greater range of conditions than those in which it naturally occurs. It grows in USDA Plant Hardiness Zones 4-8.
To learn more about trees native to the eastern U.S., or native to Virginia, see the following sources:
Identifying Trees of the East: An All-Season Guide to Eastern North America, 2nd edition (Williams, Michael D., 2017)
Common Native Trees of Virginia Identification Guide (Virginia Department of Forestry, 2016)
NATIVE AND NON-NATIVE SPECIES
It should not be confused with the non-native Common Smoketree (Cotinus coggygria), which is native from southern Europe to central China. The non-native species was introduced into America as early as 1656 and was commonly available in nurseries by 1790. It has many descriptive names including smokebush, European smoketree, cloud tree, wig tree, mist tree, and Jupiter’s beard. The Eurasian smoketree and its cultivars are sold in many nurseries and is much more commonly found in home landscapes than is the American species, which must often be special-ordered from nurseries.
What are the differences between the native and non-native trees? Both trees look very similar, although the Eurasian species has somewhat larger flowers and showier plumes. It is also smaller, growing to about 15’ in height. It grows in USDA Plant Hardiness Zones 5-8, making it a little less cold-hardy than American species. American smoketree is dioecious (male and female reproductive parts are borne on separate plants), with the male plants showing a better smoke display. The Eurasian species is monoecious (both female and male reproductive parts appear on the same tree), with no difference in smoke display between the male and female plants.
IS THE NON-NATIVE SPECIES INVASIVE?
The most favorable attribute C. obovatus is that it is a North American native. I found little documentation of invasiveness for C. coggygria. An information service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center stated that the Eurasion species doesn’t appear on any invasive lists, and probably doesn’t pose a real threat to the environment. A publication (reviewed 2014) by the University of Florida IFAS Extension described the Eurasian species as showing little invasive potential. However, the Purdue Extension included C. coggygria on a list of Invasive Plant Species in Hardwood Tree plantations, but there was no supporting information to explain inclusion on the list.
Smoketree is a member of the family Anacardiaceae, commonly known as the cashew family or sumac family. This family of flowering plants includes about 83 genera with about 860 known species. In some cases, members of the family Anacardiaceae produce urushiol, an irritant. Urushiol-induced contact is the medical name given to allergic rashes produced by various plants, including poison ivy, poison oak, and poison sumac, as well as other plants in the family Anacardiaceae (mango, Rengas tree, Burmese lacquer tree, India marking nut tree, and the shell of the cashew nut). Smoketree panicles (a much-branched inflorescence) and leaves are safe to touch, but the urushiol in the sap may cause irritation. Be sure to wear gloves when pruning.
C. OBOVATUS CULTIVARS
Although there are many cultivars sold at nurseries for C. coggygria, I found mention of two cultivars for C. obovatus:
C. obovatus ‘Cotton Candy’
This is a beautiful small tree or large shrub that grows to 18’ tall and 15’ wide. It is extremely showy, with its fascinating pink plumes in summer and red-orange fall colors. This tree does best in full sun to partial shade. It is very adaptable to both dry and moist locations. The warty brown-gray bark adds an interesting dimension to the landscape. It grows at a medium rate, and under ideal conditions can be expected to live for at least 60 years.
Developed in 1978, Cotinus ‘Grace’ is a hybrid between C. obovatus and C. coggygria ‘Velvet Cloak’. Although each flower is inconspicuous, the flower clusters borne on long panicles appear fuzzy and light, like puffs of smoke. Grace has extremely large pink panicles, 14 inches long by 11 inches wide. Its fruit is inconspicuous, but the hairy flower panicles in late summer are very showy. In spring, leaves emerge light red, darkening through the summer to dark red. In autumn, foliage turns a mosaic of red, orange, and gold. With a mature height of 15-20’, it can be used as either a small tree or large shrub and adds interest throughout the year.
American Smoketree is described as providing good cover and nesting for birds and mammals. The small seeds from the female plants are a favorite food of native finches. The tree attracts bees and butterflies but it is not described as being a pollinator magnet. Some reports claim that it is deer resistant; others describe it as moderately deer resistant.
The tree is generally disease resistant. The most serious problem is Verticillium wilt. The tree also has some susceptibility to leaf spots and rust, but these are not usually serious problems.
HOW TO USE IN THE LANDSCAPE
Long-lasting, summer “smoke” display makes this a striking accent plant. It can also be massed along a border and used as a hedge. Its size makes it a candidate for planting under utility lines. A fibrous, shallow root system makes the tree well-suited for planting next to patios or walkways.
TREES FOR 2050
The Chicago Botanic Garden is undertaking a ten-year plan to remove about 400 trees due to the emerald ash borer and to identify suitable replacement trees. Candidates should continue to thrive in a steadily warming urban environment through 2050.
Dr. Andrew Bell, curator of woody plants, and his team analyzed 50 trees in the Garden collection and found that 40 would continue to thrive under worst-case warming scenarios through mid-century. Climate-change modeling indicates that some trees—those currently growing at the northern edge of their hardiness—will actually do a little bit better in slightly warmer conditions around 2020, but by 2050, ten of the 50 trees under study—20 percent—will no longer find the metropolitan area a welcoming habitat. Even more startling, the data for 2080 projects that only 11 of the initial trees would continue to do well in Chicago and the upper Midwest.
C. obovatus was selected for inclusion on the Urban Forest Adaptive Planting List as a tree that will continue to thrive through 2050.
Although currently underused, American Smoketree would appear to be a great addition to home landscapes. It is not clear why the non-native species has become the most widely used and has come to dominate the nursery trade. There are many more cultivars of C. coggygria, and perhaps the consumer appreciates that choice. It may also be that the non-native version has been commonly available through the nursery trade since 1790, while the native version was over-harvested around the time of the Civil War. In addition, an appreciation for the eco-benefits of native plant selection is a more recent development.
Native plant organizations and tree experts laud the American native tree for its hardiness, adaptability, and resistance to disease, pests, and pollution. In addition, its magnificent fall colors are deemed to be the most beautiful of all the native North American trees. Its size and shallow roots make it an easy fit into many areas of the landscape. It may need some deer protection since there are varied reports on deer resistance. Even though there seems to be little concern right now for any problems of invasiveness by C. coggygria, choosing the native variety would seem to be a prudent choice. It may require a little extra effort to special-order the native species through a nursery or from an online supplier, but C. obovatus will reward with year-round display.
ADDITIONAL RECOMMENDED READINGS:
For additional information on trees native to Eastern U.S.: Identifying Trees of the East: An All-Season Guide to Eastern North America, 2nd edition (Willims, Michael D., 2017)
For information on trees native to Virginia: Common Native Trees of Virginia Identification Guide. Virginia Department of Forestry, 2016.
Cotinus obovatus, Missouri Botanical Garden, http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=h660
Cotinus coggygria, Missouri Botanical Garden, http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=c390
“Smokebush, Smoketree,” Virginia Cooperative Extension, https://pubs.ext.vt.edu/2901/2901-1068/2901-1068.html
“Considering Cotinus,” Kim E. Tripp, Arnoldia, 1994 Summer, Harvard Arboretum.
“Trees for 2050,” Chicago Botanic Garden, https://www.chicagobotanic.org/plantinfo/tree_alternatives
Cotinus ‘Grace’, Chicago Botanic Garden, https://www.chicagobotanic.org/plantcollections/plantfinder/cotinus_grace–grace_smoke_tree
Common Smoke Tree (Cotinus coggygria), Memphis Area Master Gardeners, http://mamgmusings.blogspot.com/2012/06/common-smoketree.html
“American Smoketree,” Look Up, Virginia! Utility-Friendly Trees https://www.plantsmap.com/organizations/452/plants/32678
American Smoketree, Ladybird Johnson Wildflower Center, https://www.wildflower.org/plants/result.php?id_plant=coob2
American Smoketree, Morton Arboretum, http://www.mortonarb.org/trees-plants/tree-plant-descriptions/american-smoke-tree#destination
Cotton Candy American Smoketree, http://plants.treetopnurserymn.com/12060004/Plant/10956/Cotton_Candy_American_Smoketree/
American Smoketree, Grow Native! Missouri Prairie Foundation, http://grownative.org/plant-picker/plant/american-smoketree/
Cotinus Coggygria, Arbor Day Foundation, https://www.arborday.org/trees/treeguide/TreeDetail.cfm?ItemID=920
American Smoketree, Cotinus obovatus, Bernheim Arboretum and Research Forest, https://bernheim.org/learn/trees-plants/bernheim-select-urban-trees/american-smoketree/
Midwestern Native Shrubs and Trees: gardening alternatives to nonnative species, (Adelman, Charlotte and Schwartz, Bernard L., 2016)
Plants Profile for Cotinus obovatus (American Smoketree), USDA Plants Database, https://plants.usda.gov/core/profile?symbol=coob2