Cotinus coggygria (Smoke Tree) is a flowering plant and one of the two species in the genus Cotinus of the cashew family Anacardiaceae. This multiple-branching deciduous shrub is also known under several other common names, including Venetian sumach, dyer’s sumach, smoke bush, cloud tree, wig tree, mist tree, Jupiter’s beard, European smoketree and Eurasian smoketree. The plant is native to Eurasia (from southern Europe to the east, covering regions of central Asia, Himalayas, and the northern parts of China), and grows at altitudes of 800 to 1300 meters.
Etymologically, the genus Cotinus is named after the Greek word for a wild olive tree, ‘kotinos’. The first historical written record of the use of the word Cotinus dates back to Pliny the Elder, the first century Roman naturalist. The specific epithet coggygria comes from the Greek word ‘kokkugia,’ loosely translated from Greek as a tree that serves as a red dye. The word coggygria was first used by Theophrastus, the student of Aristotle.
In its native habitat and in gardens, the Smoke Tree grows 5 to 7 meters tall, mostly in forming a bush, and seldom a small tree. The waxy leaves have oval shape and can be 3-8 cm long. The crown is dense, has symmetrical uniformity and a round shape. A fresh, broken leaf has a radish-like scent. The foliage becomes attractive in fall, when the color ranges across shades of of peach, yellow, orange, pink, red, scarlet and purple.
The flowers are small (diameter of 0.5 – 1 cm), five-petalled and pale yellow, with the exception of Cotinus coggygria Purpureus which has purple/pink blooms. This is also the most common and commercially available Smoke Tree cultivar. The ‘Golden Spirit’ Smoke Tree cultivar, named after its brilliant yellow foliage, has pale pink flowers.
The flowers grow in large inflorescence clasters that can be up to 30 cm long. They are bisexual or unisexual. The smoke-like effect which this plant is named after comes from the grey feathery plumes which form around the small, kidney-shaped fruits. These fine plumes are formed by the flowers that abort and elongate, forming a ‘smoke halo’, a cloud or a puff of smoke. In the folklore, the Smoke Tree symbolizes cleansing or purification, attributes associated to the idea of a flame/smoke.
As a garden plant, Cotinus coggygria (Smoke Tree) is used for shrub borders, screening hedge, patios and accent trees. It was first introduced to the USA in 1656 and, by 1790, it became quite common in the plant nurseries. Today, the plant is considered to have small invasive potential in the USA. The roots and the wood of Smoke Tree contain a yellow die, which is used in some traditional techniques of dyeing cloth and leather.
In terms of pharmaceutical use, the Smoke Tree is known in several systems of traditional medicine. In Serbia, for example, a decoction made of the bark is used in cancer treatment, while a tree extract is used to treat eye ailments and bile. Traditional Chinese medicine uses the twigs and dried leaves of a Smoke Tee as antipyretics (fever-reducing therapy).
The list of most popular Cotinus coggygria (Smoke Tree) cultivars of varieties consists of:
- ‘Royal Purple’ — a purple-leaved cultivar whose flower clusters are also purplish-red.
- ‘Purpureus’ — another cultivar with bronze-green leaves and purplish-pink flower clusters
- ‘Velvet Cloak’ — a cultivar whose purple-colored leaves turn reddish-purple in autumn
- ‘Pendulus’ — named after its pendulous branches
- ‘Flame’ — its foliage turns brilliant orange-red in autumn, and its inflorescence clusters are pink
- ‘Young Lady’ — a popular compact cultivar
- ‘Daydream’ — a green-leaved, dense cultivar with profuse production of flower clusters
- ‘Notcutt’s Variety’ (also known as ‘Rubrifolius’) — a cultivar with dark maroon-purple leaves.
How Long Does It Take To Grow Cotinus coggygria (Smoke Tree) Bonsai?
Bonsai gardeners have reported that Cotinus coggygria (Smoke Tree) plant is a rapid grower. The tree can double its foliage in half a year and, if unattended regularly, it can grow out of control. A less-favorable characteristic is that the Smoke Tree is a short-lived plant. Its life span typically ranges from 20 to 50 years. As a bonsai tree, it is unlikely to be inherited by the family’s next generation. Smoke Tree bonsai tree is typically treated as an outdoors species.
How to Plant and Grow Cotinus coggygria (Smoke Tree) Bonsai?
Cotinus coggygria (Smoke Tree) is poisonous to humans. Since the plant’s sap can irritate the skin, protective gloves and goggles should be worn while working with the tree. Smoke Tree is typically categorized a thought, an easy-to-grow plant, requiring low-to-medium maintenance in terms of placement, soil, watering and feeding.
Cotinus coggygria (Smoke Tree) bonsai can be propagated using three methods: from seeds, by layering and from softwood cuttings. The seeds are tiny. They first need to be soaked in water for 24 hours and then air-dried, before they are sown into a sandy soil, approximately 1 cm deep. Seed propagation of this plant is considered to be a rather time-consuming process. The best time to propagate Smoke Tree from seeds is in autumn. Layering can be done in spring. Softwood root cutting is best performed in summer. The cutting needs to be stripped of its lower leaves and placed in a growing medium. In general, cuttings from a Smoke Tree root easily. Rootball splitting and tissue culture are more advanced techniques for propagating a Smoke Tree.
Position, Lighting and Temperature Requirements
Cotinus coggygria (Smoke Tree) bonsai needs to be placed in full sun (at least 6 hours of direct, unfiltered sunlight per day) during the growing season. The plant can also tolerate partial shade. However, when placed in a partially sunny place, it tends to lean towards the sunny side, thus growing asymmetrically.
Ideal growth climate for a Smoke Tree is that of moderate temperatures and dry-to-average humidity. In winter, if the temperature falls below -5° C, the plan needs to be sheltered and protected from frost and icy winds. If, due to extremely low temperatures, the overground part of the plant dies, the root may still remain alive, and new shoots will reappear in spring.
Soil and Watering Needs
Cotinus coggygria (Smoke Tree) bonsai can tolerate a range of soil pH, but prefers a high pH soil. Alkaline soil helps keeping the plant healthy. The plant thrives best in infertile loam, but can grow well in most soil types, including clay, sand, shallow rocky and soil rich in organic matter. Dump, wet, soggy and poorly drained soils should be avoided.
Younger specimen need to be watered regularly and deeply. Mature plants can be quite resistant to drought. During the growing season, the plant should be watered moderately, every 10 days.
The plant has moderate aerosol salt tolerance.
Cotinus coggygria (Smoke Tree) bonsai has modest requirements in terms of feeding. A layer of compost can be given in spring. From spring until late summer/early autumn, the plant needs to be given fertilizer twice a month. Application of nitrogen can boost the growth of the foliage.
How to Care for Your Cotinus coggygria (Smoke Tree) Bonsai?
Since it is mostly a shrub, the biggest cultivation challenge is to train this bonsai grow as a tree. For the Cotinus coggygria (Smoke Tree) bonsai tree, artists recommend medium-to-large, multi-trunk or informal upright style as most suitable. Naturally, the plant has an upright, multi-stemmed habit.
Pruning and Wiring
The foliage of Cotinus coggygria (Smoke Tree) grows fast and the plant droops as it gets larger, so trimming is required throughout the entire growing season. All dead or damaged wood needs to be removed. The plant is tolerant to hard pruning, but branches should be pruned in early spring. Regular pruning helps the plant rejuvenate and maintain good shape.
To encourage a tree-like growth, all but one central stem need to be pruned away. Special care should be given to the bark, as it is thin and can easily be damaged (especially while wiring).
Cotinus coggygria (Smoke Tree) bonsai needs to be repotted in spring either annually or once in two years. Repotting can be done in basic soil mix. The plant is easy to repot, since it has a well-contained fibrous root system.
Pests and Diseases
Cotinus coggygria (Smoke Tree) is susceptible to verticillium wilt, which can cause browning of the leaves. It can further case cause whole branches to wilt and die. Verticillium wilt is mostly caused by soil that is not well-drained. All affected branches need to be immediately pruned out.
The purple variety of the plant is susceptible to mildew. Another common infestation is caused by the oblique-banded leaf-roller. If the infection is of a limited spread, it can be picked off by hand. In more serious cases, spraying with Bacillus thuringiensis is required.
When the temperatures in summer are higher, the plant can also suffer from scabs and fungal leaf spot.
The colors of a Smoke Tree can sometimes fade if the plant is left out during a particularly hot season. Coppicing (frequent and hard trimming) helps rejuvenate the color of the tree.