"'Smoke'?" she repeated, looking perplexed. I explained to her that the name comes from the spring blooms, which resemble puffs of smoke all over the plant.
Due to both their beauty and easy maintenance, smoketrees (Cotinus spp.) are a staple in American landscapes. The native variety, Cotinus obovatus, is hardy to USDA zone 4a. However, the more popular smoketrees (also sometimes referred to as "smokebushes") are those of the species Cotinus coggygria, some of which are native to China and Europe, but are mostly a group of relatively new hybrids which enjoy warm, Mediterranean-like conditions, although many are also quite winter-hardy.
By far the most desired of the smoketrees are the purple ones: ‘Velvet Cloak', ‘Purple Supreme' and ‘Royal Purple' are those readily found in local nurseries and online, and for good reason. The round purple leaves are extremely attractive and, once mature, the plant will cover itself with deep fuchsia fluffy blooms generally in late spring or early summer.
Smoketrees are extremely low-maintenance, in that they like full sun and lean soil kept on the dry side. Pretty much all the attention they require is a good pruning once the blooms are spent. Trimming the plant will result in a bushier habit and will keep the shape under control; some smoketrees can get to be quite large (12 to 15 ft.) if you let them and, as witnessed by the picture at left of my backyard purple smoketree, they can also get a bit gangly when left to their own devices.
If you want to really control their growth, however, place smoketrees in dappled shade. They'll behave themselves size-wise, although they may not bloom. At right, you can see the ‘Golden Spirit' (or ‘Ancot') Cotinus - featuring gorgeous lime green leaves - in my front yard. It's remained a respectful 3' by 3' in size but is still happy and healthy.
A dwarf green variety called ‘Young Lady' is also available if you want a smoketree but are limited in space. ‘Young Lady' stays 1 to 2 feet tall and is hardy to zone 5.
Another wonderful trait of smoketrees is their fall color. The leaves turn from orange to crimson red before dropping - a real standout in the autumn landscape. Keeping Cotinus somewhat dry will improve the intensity of the fall foliage color.
ForestFarm, a Dave's Garden Watchdog Top 5 Ornamental Trees & Shrubs company, carries several varieties of Cotinus, including many mentioned here.
Two warnings about smoketrees: They are particularly susceptible to the soil-borne fungal disease Verticillium Wilt. Chronic symptoms include small, yellow foliage, leaf scorch (marginal browning), slow growth and dieback of shoots and branches. Unfortunately, there is no treatment for Verticillium Wilt - the tree may recover on its own or it may perish. To confirm the presence of this fungus, you may need to send a sample cutting to your nearest Plant Disease Diagnostic Lab.
Lastly, because smoketrees are a relative of sumacs, they can reportedly cause skin irritation when handled extensively, so be sure to wear gloves when transplanting.
‘Golden Spirit' cotinus (in shade): TexasTam
‘Royal Purple' cotinus (leggy): TexasTam
‘Velvet Cloak' cotinus (in bloom): Dave's Garden member leisure500
‘Royal Purple" cotinus (young specimen): Dave's Garden member hczone6