Smoke Tree - Cotinus obovatus
Location: Instructional Service Center (ISC) on the West Campus. (Map)
This tree is in the Anacardiaceae (Sumac or Cashew Family). The family is medium-sized with 70 genera, only three of which are native to Texas. The two genera other than Cotinus are Rhus (Sumacs) and Toxicodendron (Poison Ivy and Poison Oak). Some important food plants in this family are Cashew nuts, Pistachio nuts and Mangoes. Cotinus comes from a Greek word that means reddish wood and the specific epithet, obovatus, refers to the egg-shaped leaf. This tree was named by a naturalist, Constantine Samuel Rafinesque (1783-1840), who came from Constantinople and lived in Kentucky.
Cotinus obovatus is a deciduous shrubby plant or a small multi-trunked tree that may rarely get to a height of 32 feet. The tree form of this plant has an open, rounded crown. According to some sources, this tree is said to be a relic tree from the Miocene Epoch that was approximately 25 million years ago. In Sargent’s Manual of the Trees of North America published in 1905 (vol. 2 p. 658), the author states that C. obovatus grew in valleys along the upper Guadalupe and Medina Rivers “and was abundant as a small shrub and spread over many thousands of acres of the mountain canons, and high hillsides in the neighborhood of Spanish Pass, Kendall County, Texas.” There are remnant populations on the southern end of the Edwards Plateau. The closest population to the north is in Eastern Oklahoma and Northeastern Arkansas; the closest one to the east is in Alabama.
The simple leaves are egg-shaped with the broader portion of the blade at the apex and the petiole attached to the narrower end (base). The young leaves are purple and are covered with fine silky hairs as they begin to unfurl. At maturity the leaves have wavy margins and are dark green on the upper surface. The underside is a pale green with pubescence (fine hairs) on the midrib and primary veins. The leaves are arranged alternately along the stems.
Cotinus obovatus flowers are a light pink color and are arranged in loose terminal panicles. There are few flowers in each panicle (infloresence). The clusters of pastel pink flowers covering the tree in the early spring give the appearance of wisps of smoke especially in a gentle breeze, thus the common name, Smoke-tree. The kidney-shaped brown fruits (drupelets)which are supported on the purple pubescent pedicles after the blossoms have fallen also give a smoke-like look to the plants when viewed from a distance. The flowers are pollinated by insects. Smoke trees are primarily dioecious (staminate and pistillate flowers are on separate trees). However, they may rarely be polygamous-dioecious in which case there may be some perfect flowers or flowers of the opposite sex on a tree that is predominately unisexual.
The Smoke-tree grows best in full sun but can tolerate some shade. Well-drained alkaline soil is a necessity for this plant that is both drought-tolerant and disease-resistant. If the soil is too rich or if the plants are over watered or over fertilized, the wood becomes weak and brittle. In its natural habitat the wood is very strong and durable and has been used to make fence posts and tool handles. The seeds of these plants are not suitable for propagation; cuttings are a better way. Another interesting characteristic of this plant is that the wood contains a yellow-orange pigment that is soluble in water and can be used in dying fabrics. This dye was much in demand during the Civil War.
This is a tree for “all seasons” with the beautiful spring blooms and the equally-beautiful fall color. The variety of bright yellow, orange, red and purple all on the same tree in the fall make it a good choice for an ornamental in any landscape.