If you've got a spot in the yard for something really eye-catching and a little different, consider smoke bush (Cotinus). The colorful foliage of this unusual ornamental is attractive throughout the season, but really heats up in fall, deepening to brilliant shades of purple, red, or orange-yellow, depending on the variety. As the large, loose clusters of tiny greenish flower blossoms fade, the flower stalks get longer and by midsummer are covered with fuzzy purple or pink hairs. These feathery trusses look like puffs of smoke -- hence the common name smoke bush or smoke tree. Even with these showy blossoms and vibrantly colored leaves, smoke bush is an easy plant to work into the landscape because it combines so readily with other perennials.
Striking as a single plant, it is spectacular in a group. "This plant is definitely underused," says Alan Summers, owner of Carroll Gardens, a retail and mail-order nursery in Westminster, Maryland. "It just marches out of here. Once people see it, they take it home."
Smoke bush is hardy in virtually all regions of the United States from USDA Hardiness Zone 4a through 11. However, it's most prized in the colder areas where few other plants can compete with its dramatic foliage color.
You'll see smoke bush described in catalogs and garden references as both a shrub and a tree. Left to its natural inclinations, it will grow into a tree. The Eurasian species, Cotinus coggygria, reaches a height of 15 feet; C. obovatus, a native of the southeast, is even taller, reaching 25 to 30 feet. In the garden, smoke bush can be trained as a single- or multi-trunked tree. "But that's a lot of work," says Summers. Treat it as a large shrub, he advises, and you'll have a full, nicely rounded plant that's easily maintained.
Another recommendation from Summers is to start with a named variety. Bill Funkhouser, assistant director of horticulture at Wayside Gardens in Hodges, South Carolina, agrees. "Although the American native has good fall color and I'd like to see it grown more," he notes, "you want the best show you can get out of your plants, and a selected variety will give you the best blooming, the best form and the most consistent coloration."
There are several fine selections of C. coggygria available; the shades and intensity of the colors can vary somewhat depending on soil conditions and climate.
'Velvet Cloak' has reddish purple leaves that hold their color well through the season, turning to a brilliant deep red in fall. It produces many purply pink "smokes." "It's just spectacular all season long," says Summers.
The leaves of 'Royal Purple' start off red, deepening to a rich purple that stays vibrant through the summer, then changing to shades of red, yellow, and orange in fall. "It's a little more compact than some of the other cultivars," notes Funkhouser, "and the foliage doesn't fade." The blossom clusters are purple.
The hardiest of the purple-leaved smoke bushes, 'Nordine', has large, pinkish blossoms and purplish red leaves that turn a rich green or orange-yellow in fall. "By fall, the blossom clusters are huge and showy, and the leaves have good color," says Summers.
Hardier still are the green-leaved smoke bushes, and 'Daydream', with blue-green leaves that turn red-orange in fall, is a very attractive variety. Its pink smokes stay showy for a long period of time.
A pink hybrid, 'Grace', is now available in the United States. A cross between Cotinus obovatus and 'Velvet Cloak,' it has won several awards in England. "The 4- to 6-inch leaves are about 1/3 larger than those of other cultivars and the huge smokes are almost a fluorescent pink," says Rick Eggimann, owner of Hollandia Gardens, wholesale growers in Hubbard, Oregon. The purplish red foliage turns red-orange in fall. 'Grace 'is a very vigorous grower, however, and tends to be lanky rather than bushy, he notes. It requires some vigilance with the pruning shears during the growing season to keep it looking good.
Whether you plant one smoke bush or group several together, choose the location carefully. "It's too large to be a foundation plant, and I wouldn't simply park it in the middle of the lawn as a single specimen, either," says Alan Summers. "Think of it as a lilac in terms of placement. It's a good screening plant and works well on the edge of the property, perhaps dressed down with another shrub.
As with any shrub, buy your plant from a knowledgeable retail or mail-order nursery. You'll probably find the greatest selection in spring, but smoke bush is available throughout the season and fall is an excellent time to plant shrubs in most areas of the country.
If you purchase yours at a local nursery, you'll find it either in a container, or balled-and-burlapped. The container-grown plants can be anywhere from 10 inches to 2 to 3 feet in height, depending on the age of the plant. A balled-and-burlapped plant is older and therefore larger (typically 4 to 5 feet tall), but more expensive. Select a disease-free, healthy plant, and don't be put off by leaves and blossoms that look small -- they may be somewhat stunted if the plant has been container-grown, but will reach normal size the following season.
Catalogs describe their offerings by height or size of container; plants from a 1-gallon container are usually 1 to 2 feet tall, and those from a 2-gallon container a foot or so larger. Your mail-order plant will typically arrive with plastic wrapped around its roots and a small ball of soil; some companies ship the plant in the container.
The smoke bush's few requirements are full sun and a well-drained soil that's low in fertility. In fact, it thrives in dry, rocky locaions. Proper drainage is critical to avoid problems with Verticillium wilt, which will cause sudden dying back of the branches. If the plant does become infected with this soilborne fungus, it must be replaced. Otherwise, smoke bush is relatively disease- and insect-free. In California, it is valued for its resistance to oak root fungus (Armillaria mellea).
After transplanting, water the shrub during dry spells to help it get established. Alan Summers recommends fertilizing lightly in spring with a handful of organic plant food, especially for the first two or three years. "But it doesn't like a rich soil," he cautions. If you overfertilize, you may not get the intense fall color and the growth will be coarse and lanky. "Also," notes Bill Funkhouser, "where the plants are growing along the edge of a lawn, be especially careful not to overwater and overfertilize the grass." The shrubs could keep growing into fall and get damaged by cold weather.
Though hardy to -30° F (zone 4a), smoke bush may die to the ground or snowline at the colder limits of its range. Elsewhere, leaves and stems might be nicked by frost.
You can also cut the shrub to the ground in fall and mulch it. In fact, this treatment can be effective no matter where you live, notes Harold Greer of Greer Gardens in Eugene, Oregon, a nursery that offers both species and a good selection of varieties of smoke bush. "It's a fast grower, so in one season you'll get a dynamic-looking plant full of healthy new growth that's saturated with color," he says. It flowers on second-year growth, however, so you won't get the "smokes." Otherwise, some simple rejuvenation pruning in spring to cut out the oldest, woodiest stems is all the shrubs need.