Smoke bush: pruning, propagation & the most beautiful varieties

The smoke bush shows its best side in summer as well as in the colder seasons with colourful autumn foliage and light clusters of fruits.

Both the foliage and eponymous seed heads of the smoke tree (Cotinus coggygria) contribute enormously to its high ornamental value. Its appearance immediately catches the eye of every visitor to the garden. Today, we’ll explain how to prune and propagate the smoke tree and describe a few of the most beautiful varieties of smoke tree.

Smoke tree: properties and origin

Some synonyms by which this ornamental shrub is still known include wig tree, smoke bush and dyer’s sumac. It belongs to the sumac family (Anacardiaceae), which includes the vinegar tree (Rhus). The original distribution area of the perennial smoke tree is very extensive. The plant has its roots in the Mediterranean region, southern Europe, southwestern Asia, northwestern India, as well as China, Pakistan and Nepal. Meanwhile, Cotinus coggygria has even become naturalised sporadically in the warm regions of Germany and parts of the UK. Its natural habitats are characterised by poor to moderately nutritious, calcareous soils that have a coarser, sometimes stony texture. The large shrub is found on dry, warm slopes from lowlands to mountainous heights.

The deciduous smoke tree grows bushy, spreading and sparse. It can reach heights and widths of 3 to 5 m – but there is also a variety called the dwarf smoke bush, which can be easily grown in a container. The smoke tree is only hardy down to about -20° C, which should be considered when choosing a location. The bark of this undemanding ornamental shrub is grey-brownish and slightly cracked. The ovate, smooth and entire-margined leaves of the smoke bush are alternately arranged. The foliage of the original species is green – depending on the variety it can also be red, dark red or yellowish-green to golden yellow. In the autumn, the leaves turn a handsome yellow-orange to scarlet. The small, inconspicuous, yellow-green flowers of the smoke tree have five petals and are arranged in larger, slightly hairy, loose panicles. They usually appear from June to July and eventually develop into the namesake’s cloudy seed pods, which often continue to have an ornamental effect into December due to their stable structure.

The most beautiful varieties of smoke bush

There are several varieties of smoke tree, which differ mainly in their growth size and colour. Below we present a selection of the most beautiful varieties:

• Cotinus coggygria ˈRoyal Purpleˈ: this is a very popular, rather slow-growing variety that reaches a height and width of up to 3 metres. The foliage is intensely dark to black-red, and the flower panicles are yellowish to cream in colour.

• Cotinus coggygria ˈGolden Spiritˈ: this variety has a very different effect with its golden yellow foliage and reddish tinted flowers. It grows around 2 to 2.5 m tall and 1.5 to 2 m wide. The fruit clusters of this variety are reddish-brown.

• Cotinus coggygria ˈLillaˈ: this low-growing and compact version of ˈRoyal Purpleˈ is limited to a height and width of about 1.5 m, making it suitable for smaller gardens or planting in containers. The leaves are dark reddish-purple and the flowerheads are yellow green to red.

• Cotinus coggygria ˈSmokey Joeˈ: this medium-growing cultivar bears green foliage and pinkish-reddish fruit clusters. The height and width grow up to 2.5 m.
• Cotinus coggygria ˈYoung Ladyˈ: the flowers of this low-growing, green-leaved variety are yellow, pink in colour while the fruit decoration is white, brown. It can also reach a height and width of 2.5 m.

Planting a smoke bush: location and method

A red smoke tree should be placed in a warm, sunny location, as only then will the foliage display its colours to the full intensity. Smoke tree varieties with green or golden yellow leaves develop well even in partial shade. A sheltered place should definitely be chosen in regions with harsh winters. As for soil conditions, the smoke tree is adaptable and makes few demands. Moderately nutrient-rich, dry to moist soil that is slightly acidic to highly calcareous and well-drained is suitable – smoke trees grow best on rather poor soil.
However, compacted, heavy and very moist soil must definitely be loosened and mixed with many stones and quartz sand to prevent Verticillium wilt.

You can also add some lime to the soil to further improve the site for the smoke tree. This is particularly advantageous for the smoke tree. To properly apply and find the appropriate dosage, you should first determine the pH of the soil and identify your soil type.

September and October are particularly good months for planting, but it is also possible as early as spring after the Ice Saints. The diameter of the planting hole should be dug twice the size of the root ball of the ornamental shrub. Very sandy soils are enriched with high-quality planting soil or a little compost. Our peat-free Plantura Organic Enriched Compost is suitable here, which makes the soil more fertile for a longer period and stimulates biological activity. The smoke tree should then be placed in the hole – not too deep, rather at ground level. Once the planting hole is filled with soil again, press the substrate a little and water the tree well.

Classically, red smoke tree is planted mainly as a solitary shrub, which makes it stand out particularly well. However, the somewhat narrower ˈGolden Spiritˈ smoke tree allows a small hedge to be created as a privacy screen. In this case, a planting distance of around 1 metre is recommended. If other shrubs are planted near the smoke tree, the distance should be at least twice as large.

If you want to cultivate the dwarf smoke shrub as a container plant, you should use a planter with a capacity of at least 30 litres at the beginning, and later, when the shrub has grown larger, 50 litres. It should also have a drain for excess irrigation water. A drainage layer of expanded clay should be placed at the bottom of the container. Finally, fill the pot with a high-quality planting soil mixed with at least 30% sand to improve permeability.

What goes well with the smoke tree? If you want to showcase your smoke tree alongside other plants, you can use monk’s pepper (Vitex agnus-castus) and an ornamental grass such as Chinese silver grass (Miscanthus sinensis). Both let the flamboyant smoke tree steal the show, developing attractive flowers and seed pods at different times to complement the smoke tree’s cloudy seed pods. The combination of a light-leaved smoke tree with the ‘Kesselringii’ black-stem dogwood (Cornus alba ‘Kesselringii’), purple dogwood ‘Sibirica’ (Cornus alba ‘Sibirica’), or red dogwood (Cornus sanguinea) is equally as interesting. Around-leaved and also variegated-leaved Berberis species also represent other harmonious planting partners.

What is the ideal location for the smoke tree? The ideal location is warm and sunny, with at least partial shade and sheltered in regions with harsh winters. The dry to damp and nutrient-rich soil must be highly permeable.

Smoke bush care

Once the ornamental shrub is well established in the garden, it proves to be not only reliably hardy but also extremely resistant to heat and drought. In addition, the plant does not require a particularly high level of nutrients and does not necessarily require regular pruning. So, as you can see, caring for the smoke tree is not very laborious.

Pruning a smoke tree

As already mentioned, the smoke tree does not require regular pruning. It forms a beautiful shape and blooms even without proper care. To counteract a strong spread, the ground-lying shoots can be removed directly at the base. Branches that grow toward the centre of the bush or cross over can also be cut off at the base. The tree also copes well with more vigorous pruning but do not expect it to bloom the following year. Smoke trees can even be cut back to the trunk every few years.

When to prune the smoke tree? Due to its good pruning tolerance, you can prune the smoke tree almost all year around – just avoid pruning in hot, dry midsummer periods and during frost.

Fertilising and watering a smoke bush

Incorporating a single application of compost in the spring should fully meet the nutrient needs of the smoke tree in open ground. If the nutrients from the substrate of the containers are already depleted, you can re-fertilise it about every four weeks with a liquid fertiliser for flowering shrubs.

Tip: a mulch layer of autumn leaves or grass clippings not only retains moisture in the soil for longer but also provides some nutrients.

Watering is particularly important for newly planted specimens and smoke trees in containers. After planting in the open ground, it is especially important to provide constant moisture to support growth. Even during periods of drought, the newcomers should definitely be provided with watering in the first year. However, it is always important to avoid water logging – this creates problems for the roots and increases the risk of infestation with Verticillium wilt, which can be fatal for the shrub. Once the shrub is well established, it can then cope with drought in open ground.

Overwintering a smoke bush

The smoke tree and its cultivars, as already mentioned, are hardy down to about -20 °C, which should be sufficient in most cases. However, in particularly harsh locations, additional protection is recommended. Winter protection is also necessary in the first one to two years after planting, as well as if cultivated in a container. The tree trunk can be covered with various materials such as leaves, or brushwood and the young shrub can be wrapped with fleece or jute. The container may be wrapped with bubble wrap but if you do not want to risk freezing through the root ball, move your smoke tree in its container to frost-free, yet sufficiently cool winter quarters. Do not forget to water a little occasionally so that the root ball does not dry out completely.

Propagating smoke bushes

A more promising method than propagating the smoke tree by seed is propagation by cuttings or shoots. We describe below how to do this.
For cuttings, do not use the youngest nor oldest branches. The time is right if the branch can be bent a little and then breaks. Cuttings should be taken in summer from July to August, preferably in the morning. Make the cut below a leaf node and take sections around 8 to 12 cm long. They should be kept cool and moist until planting. After removing the lower leaves and a little of the bark at the bottom, the wound must be dipped in a rooting hormone because the smoke tree struggles to form roots on its own. You can now put the cuttings in prepared pots with a permeable, moist substrate. To maintain moisture, a plastic bag can be placed over the pot. After a few weeks, enough roots should have formed to move the plants to a larger pot.

Tip: half of the remaining leaves can be removed to reduce the transpiration rate of the cuttings. Thus, the section loses less moisture.

The method of propagation via smoke tree shoots occasionally even happens by itself by forming roots from old shoots lying on the ground. These parts can then be removed from the mother plant and planted. However, the process can also be performed by yourself. To do this, plant shoots that are at least one year old in the ground in the spring and attach them there with a hook. The shoots should still protrude from the ground about 30 cm and can be scratched to promote root development in the place that should be under the ground. Finally, keep the soil evenly moist. In the autumn, after sufficient root development, the shoot can be separated from the mother plant and planted in a new location.

Storage, use and effect

The leaves and wood of the smoke tree can be used for dyeing fabrics made of wool or silk. Use the harvested parts immediately or dry the leaves and wood to store. Smoke tree leaves are used in Russian traditional medicine to treat burns or poisoning. According to a study based on experiments, it was found that the concentration of the dye fisetin in the smoke tree has beneficial effects for humans. In fact, it is supposed to promote information retention in the brain, which would result in a better memory.

Are smoke bushes poisonous?

Due to its relationship to the toxic oak-leaved poison ivy (Toxicodendron pubescens), also known as poison ivy, skin-irritating properties have also been suspected upon skin contact with smoke trees. However, this assumption was not confirmed even in people sensitised to the contact allergen of poison ivy. However, if you know your skin is very sensitive, you can avoid potential skin irritation by wearing gloves when pruning the shrub. The smoke tree is not poisonous but, as an ornamental shrub, it is also not suitable for consumption.

An ornamental shrub with similarly rich coloured foliage is the strawflower (Loropetalum chinense). In addition, the plant’s showy flowers contribute enormously to its attractive appearance.