Plant Spotlight: Smoke Tree
By Eric Larson
Magnificent in yellow, orange, amber, red and reddish-purple, this tree inspires accolades from all quarters. To quote Michael Dirr, “In fact, it may be the best of all American shrub/trees for intensity of color.” The image above was taken on this rather cloudy dreary day, but the great foliage color pops out at you as you descend the hill to Greeley Lab. It should be noted that the wildflower garden in the background is the home of last week’s plant, Cosmos bipinnatus. This bed is anchored by a Sourwood (seen in background) which will have a vivid dark red to purple fall color in a week or so, and on the other end is Rhus typhina ‘Tiger Eyes,’ the Golden Staghorn Sumac, with a yellow fall color. The leaves of the Smoke-tree stay on the tree for up to three or four weeks, so this adds to the delight in fall: many of the most colorful are quick to drop their leaves as if saying “Such beauty can only last so long: enjoy me while you can.” Our tree is saying, “Check me out tomorrow: I’ll look even better.”
Cotinus obovatus is hard to find in the nursery industry. Broken Arrow said they had a few but they weren’t big enough to sell. Those who bought the trees for the new Forestry Building haven’t been reading the column, but it’s always better to think big, but plant small. This mantra has been repeated in these pages until readers have actually created drinking games based on the number of times the phrase shows up in print. Other than those small ones at Broken Arrow, I don’t know of a single nursery locally that will sell you an American Smoke-tree. The other species is more readily available, especially the cultivars including C.coggygria ‘Velvet Cloak,’ ‘Royal Purple’ and ‘Golden Spirit.’American Smoke-tree, also called Chittamwood in some locales, is a small growing tree or large growing shrub. It tops out at around twenty or twenty-five feet. The national champions are thirty-nine feet high and thirty-eight feet wide. This reflects their general shape, which is rounded and broad. They grow nicely to fifteen feet or so, but they slow down in growth rate after that. They prefer full sun or light shade for exposure, and are tolerant of soils, often growing in high pH, calcareous and rocky thin soils. In fact, the richer the soil, the more ungainly their growth habit. This is illustrated well here at Marsh Gardens, where the one in the photo below is on a hillside in thin soil, while the other resides below in a well-watered deep rich topsoil. Its shape is much more awkward, but you know a father must love the ugly duckling as much as he loves the supermodel. So I prize them both for their individuality.