Smoke Tree

The Smoke Tree (Cotinus coggygria) grows on rocky and dry slopes in light scrubland. It is found in the eastern Mediterranean, on the Balkan peninsula and in Asia. It is also naturally found in South Tyrol and Ticino. The Smoke Tree is part of the cashew or sumac family (Anacardiaceae), so is related to the staghorn sumac. Thanks to its fine growth, it is popular among hobby gardeners as a solitary shrub.

The Smoke Tree is an adaptable, medium-sized shrub that grows up to 10 to 16 feet tall. As it ages, it often spreads and bows its branches down. It can grow as broad as it is tall. Its growth is somewhat spreading but upright. This decorative shrub forms ochre-colored branches and yellow-barked pithy stems covered with lots of lenticels.

The leaves of the deciduous Smoke Tree are alternate and obovate to eliptical in shape. They grow to around 1.18 to 3.15 inches long and are very thin. The leaves appear relatively late but in a fresh shade of green. In fall, they turn bright orange to scarlet red.

The individual flowers are just 0.31 inches in diameter so are easy to overlook. The large and very fine yellow-green inflorescences, however, are very striking. They form in June and July and often cove the whole shrub - from afar, it looks like yellow-green cotton candy pierced with small sticks. Smoke Trees are dioecious, so there are male and female plants.

The fruits of the Smoke Tree are striking bushels that cover the whole shrub with a smoke-like shroud of fine fibers in late summer - hence the unusual name. These “fibers” are the fine, feather-like stems of the unfertilized flowers.

The Smoke Tree likes it sunny and warm. It also thrives in partial shade but it will only unfurl its full glory in a location with full sun.

This decorative shrub has minimal needs when it comes to soil, and it has proven itself to be very adaptable. In principle, it will grow in all cultivated soils. It does, however, prefer limey, moderately nutrient-rich, dry to fresh and permeable soils. In heavy, compacted and moist soils, it can be susceptible to verticillium wilt, an incurable and usually fatal fungal disease.

Shrubs available to buy are increasingly grown in pots and containers - and the smoke tree is no exception here. If the ball is root bound, you can plant it out at any time of year. Shrubs that have been planted out with root balls should only be planted outside of their growing season. It’s important to carefully consider where your smoke tree should be planted as shrubs that have established are difficult to move.

Generally, spring - and fall in zones with mild winters - is a good time to plant smoke trees. Just make sure that the soil is not too wet or compacted and used coarse sand to improve heavy soils. The planting hole should be at least twice as wide as the ball’s diameter. Never plant the root ball too deep.

When planted out, the smoke tree is reliably winter hardy and very resistant to drought and heat. It even does well in the intense midday sun. It can manage with few nutrients so does not require regular fertilization. It is among the few shrubs that prefers mineral soils - so you should avoid adding compost. You will have to water young plants in dry conditions if they have not yet established.

The Smoke Tree can be pruned all year round as it is very tolerant of pruning. It doesn’t need regular pruning to bloom reliably and form a lovely crown. If it spreads too much, you can remove any rooting shoots along the ground directly at the root. If older specimens are drastically cut back, they may fail to flower in the following year. Red-leafed varieties such as “Royal Purple” have beautiful, almost metallic new growth. If you’re not too bothered about the flowers, you can cut these cultivars back more drastically for beautiful foliage in late winter.

Smaller, freshly planted plants should be given leaf mulch and pine branches in fall as winter protection if they are to survive serious frost. Smoke Trees are winter hardy down to -4 degrees Fahrenheit, which is rarely put to the test in temperate zones.

The Smoke Tree is especially suited to individual planting on lawns - with its unique fruiting stems and its leaves varying from light green to deep red depending on the variety - as well as its impressive fall colors, it will draw the eye in any garden or park. This decorative shrub can also be combined with fall shrubs, decorative grasses and other fall-coloring woody plants. The Smoke Tree also makes quite the statement in larger rockeries, while its robust nature and exceptional drought tolerance make it ideal for growing in large containers on patios or roof terraces.

The Red Smoke Tree (Cotinus coggygria “Royal Purple”) is even more popular than the wild green variety. It grows up to 10 feet tall and wide. Its leaves boast a metallic sheen and an intense shade of black-red. It can be used to create a unique contrast with green lawns and dark green hedges. In fall, it turns orange to bright, fiery red.

The Smoke Tree can be propagated by sowing seed in spring or directly after the fruiting stems mature in fall. Layering in spring offers better chances of success, however. Cover a side shoot in soil and secure it. The final 12 inches of the shoot should protrude from the soil. In fall, when the layered shoot has rooted, you can separate it from the parent plant and move it to another location. The plant often propagates itself through layering as its side shoots root when in contact with the ground. These can be removed in spring and planted out somewhere else.

As already mentioned, this decorative shrub can fall foul to verticillium wilt in unsuitable locations. The Smoke Tree reacts to this fungal infection with stunted growth and wilting leaves, as the fungus blocks the shoots’ pathways. Radical cutting back can sometimes help but the infected plant often dies. Powdery mildew is sometimes a problem, although doesn’t cause much damage.