Smoketrees (Cotinus spp.) derive their common name from their wispy, filamentous flowers, which appear like puffs of smoke when viewed from a distance. Because they are very easy to grow and add unique beauty to suburban landscapes, smoketrees are very popular ornamentals, often planted as borders or hedges.
A Tale of Two Species
American smoketrees typically grow slightly larger than the European species do, in terms of both height and spread. They also feature larger leaves than their European counterparts, but the European species usually bears denser flower heads than American smoketrees.
While the two have different geographic ranges (American smoketrees grow throughout the southern United States, while European smoketrees are found through southern Europe, east as far as the Himalayas), they are both commonly planted in each other’s respective range. However, European smoketrees are the more commonly used ornamental of the two species and they are available in a greater number of cultivars.
Traits of the Trees
Smoke trees can reach heights of 20 to 40 feet, but many are little more than shrubs and few reach heights greater than 15 feet. Their flowers grow as 6- to 12-inch-long panicles, which vary from pink to white in color. Most pollination probably occurs with the help of insects, such as bumblebees. Because most of the nectar produced by smoketrees is easy to access, a wide variety of insects feed upon them.
Smoketrees first bloom in the spring, but they can continue bloom for the duration of the summer. Once cross-pollinated, smoketrees produce small, dry fruits, technically termed drupes. The fruit do not appear to have a significant value to wildlife, nor do they cause a substantial litter problem.
In addition to their beautiful flowers, smoketrees often bear attractively colored leaves, which are particularly gorgeous in the autumn, when they turn brilliant red, yellow or purple. Smoketrees also bear exfoliating bark and – at least on older specimens – twisted, gnarled trunks, giving the trees further visual appeal.
Unlike many other trees and shrubs, which thrive in highly fertile soils, smoketrees often grow best in relatively infertile soils. While they will grow quickly in fertile soils, this tends to shorten their lifespans.
Additionally, those grown in highly fertile soils tend to produce a less-attractive, sparse growth habit, rather than the compact, dense habit attained by those grown in infertile soils. Aside from those that are too fertile, smoketrees adapt well to most soils. They exhibit moderate drought tolerance, but can also cope with periods of intense rain.
Smoketrees in Southern California
Most authorities recommend planting smoketrees in USDA Hardiness zones 5 through 8, but smoketrees usually thrive in southern California landscapes. Few smoketrees succumb to pests, although they are susceptible to Verticillium wilt. Smoketrees require relatively little supplemental irrigation and they are rather drought tolerant. The plants work well in relatively small areas, and they rarely produce damaging surface roots.
Much of their size and growth habit depend upon how they are maintained – some homeowners prefer for the plants to take on a tree-like form, whereas others prefer to keep the trees small and shrub-like. Some even coppice the trees, causing them to produce a flourish of dense, young growth. However, this practice reduces the number of flowers that develop in the coming season.
Cultivars featuring dark leaves and bright pink to purple flowers are particularly favored by gardeners and homeowners.