Smoke bush is grown for two effects that no other shrub quite matches. The first is the foliage: rounded leaves like coins, in deep plum purple on the best known forms, that glow when the sun is behind them and turn orange, scarlet and crimson before they fall. The second gives the plant its name. In early summer the flower heads spread into soft, hazy plumes that hang over the shrub like a puff of pink or purple smoke. Smoke bush is tough, frost hardy and undemanding in the right climate, which is a cool or temperate one. This guide covers where it grows well, the forms we sell, and the pruning choice that decides whether you get the smoke or the biggest, richest leaves.
Quick facts
| Feature | Detail |
|---|---|
| Botanical name | Cotinus coggygria and its hybrids; also called smoke tree |
| Type | Deciduous shrub or small multi-stemmed tree |
| Size | 3 to 5 m tall and 3 to 4 m wide unpruned; 1.5 to 2 m when cut back hard each year |
| Position | Full sun for the best leaf colour and the most plumes |
| Climate | Cool and temperate districts; leaf colour and health decline in humid subtropical gardens |
| Frost | Very hardy |
| Soil | Any well-drained soil, including poor and stony ground; dislikes wet feet and rich feeding |
| Plumes | Late spring to midsummer, on wood at least two years old |
| Autumn colour | Orange, scarlet and crimson, strongest where autumn nights are cold |
What makes the smoke
The flowers themselves are tiny, yellowish and easy to miss. They open in late spring in large, branching clusters at the ends of the stems. Most of the flowers in each cluster never set seed. Instead, their stalks lengthen and grow a coat of fine, silky hairs in pink, purple or buff, and the whole cluster turns into a loose, feathery plume up to 20 cm long. From a few metres away the shrub looks as if it is wrapped in haze. The plumes last for weeks, fading slowly through summer.
Two things follow from this. Plumes form only on wood that is at least two years old, so a shrub that is cut hard every winter never smokes. And a young plant may take two or three years in the ground before it puts on a real show.
A note on the name. In Western Australia, smoke bush usually means Conospermum, a native shrub with woolly grey-white flowers. It is a different plant with very different needs. This guide is about Cotinus, the garden shrub from southern Europe and Asia.
Where smoke bush grows well
Cool and temperate districts. Smoke bush is at its best wherever winters are cold and summers are warm and not too humid: Victoria, Tasmania, the ACT, the tablelands and inland slopes of New South Wales, the Adelaide Hills and plains, and the south-west of Western Australia. It takes heavy frost without damage, copes with summer heat if it has had time to establish, and colours brilliantly in autumn. It is one of the more reliable sources of purple foliage for a cold garden, and it sits well with the trees in our autumn colour range.
Sydney and similar warm temperate gardens. It grows, and grows quickly, but expect less: the purple fades towards green in the heat of summer, autumn colour is brief, and humid weather brings leaf spots and mildew. Give it full sun and an open, breezy position.
The subtropics and tropics. Smoke bush is not a plant for Brisbane or the Queensland coast. Without a cold winter it grows weakly, and summer humidity ruins the foliage. For purple leaves in a warm, humid garden, a Chinese fringe flower is the better choice, and our loropetalum care guide explains how to grow one.
Smoke bush is deciduous, so it is bare from late autumn to early spring. Our guide to evergreen and deciduous trees explains how to use that in a garden design: winter sun reaches the house and the plants beneath, and the new leaves in spring are a fresh event each year.
Smoke bush varieties we sell
The whole range is in the smoke bush collection.
Purple smoke bush. The classic purple smoke bush has plum-purple leaves through spring and summer and pinkish-purple plumes, then turns red in autumn. It is the one most people picture.
Royal Purple. Royal Purple is the darkest selection, with deep wine-purple leaves that hold their colour better through summer than other forms, and scarlet autumn colour. It is the pick for foliage contrast against silver, lime or blue plants.
Grace. Grace is a vigorous hybrid between the European smoke bush and the American smoke tree. It has the largest leaves and the biggest pink plumes of the group. The leaves open wine red, deepen through summer and finish orange-scarlet. It reaches 4 to 5 m if left unpruned, so give it room or plan to cut it back.
Flame. Flame is the one chosen for autumn. Its leaves are green through summer, with pink plumes, then the whole plant turns brilliant orange-red. Because it is green in summer it blends easily into an existing garden.
Planting and care
Position. Full sun. In shade the purple forms turn a muddy green, the plant grows lanky and there are few plumes. Allow for the mature spread of 3 to 4 m unless you intend to prune hard each year.
Soil. Smoke bush is happiest in ordinary to poor soil that drains freely, and it handles stony, sandy and alkaline ground. It is a good shrub for the difficult, dry bank where richer plants fail, as our guide to plants that thrive in poor soil describes. The two things it will not stand are waterlogged ground, which rots the roots, and heavy feeding, which gives soft, floppy growth, fewer plumes and duller autumn colour. On clay, plant on a mound.
Planting. Plant in autumn or winter in cold districts so the roots settle before summer. Dig a hole twice the width of the pot and the same depth, set the root ball level with the soil surface, backfill with the soil you dug out, and water in. Mulch 5 to 7 cm deep, keeping the mulch off the stems. Space plants 2.5 to 3 m apart for an informal screen.
Watering. Water weekly through the first two summers. After that a smoke bush is drought tolerant and needs a deep soak only in long dry spells. Over-watering an established plant does more harm than neglect.
Feeding. A light dressing of compost or a small handful of slow-release fertiliser in early spring is enough. On reasonable soil, do not feed at all.
Pruning: smoke or leaves
There are two ways to prune a smoke bush, and they give two different plants. Decide which you want before you pick up the secateurs.
For plumes and a large shrub. Prune very little. In late winter, while the plant is bare, remove dead, damaged and crossing branches and shorten any stem that spoils the shape. That is all. The framework of older wood stays, and it is this wood that carries the plumes in early summer. Over time the shrub becomes a broad, rounded small tree with attractive flaky bark.
For the biggest, darkest leaves and a compact plant. Cut it back hard. In late winter, shorten every stem to two or three buds above a low framework 30 to 60 cm high. Gardeners call this coppicing. The plant responds with strong, straight shoots 1.5 to 2 m long carrying leaves up to twice the normal size and of the richest colour. There will be no smoke, because all the growth is new. Start this only once the plant has had two or three years to establish, and give a coppiced plant a mulch of compost each spring to fuel the regrowth.
A middle path is to cut a third of the oldest stems to the base each winter. You keep some plumes and renew the plant gradually.
Wear gloves when pruning. Smoke bush belongs to the same plant family as the mango and the cashew, and its sap can irritate sensitive skin. Our pruning guide for beginners covers how to make a clean cut above a bud.
Common problems and fixes
Purple leaves turning green. Too much shade, too much fertiliser, or summer heat in a warm district. Move or open up the position, stop feeding, and choose Royal Purple, which holds its colour best.
No smoke. The plant is too young, or it was pruned hard in winter, which removes the older wood that flowers. Leave it alone for two years.
A branch wilts and dies while the rest looks healthy. This points to verticillium wilt, a soil fungus that blocks the water-carrying tissue. Cut the affected branch out well below the damage, clean the secateurs afterwards, water the plant in dry weather and avoid root disturbance. A badly affected plant should be removed, and another smoke bush should not go in the same spot.
White powder or dark spots on the leaves. Powdery mildew and leaf spot appear in humid or crowded conditions. Improve air movement, water at the base and rake up fallen leaves in autumn. See our guide to common plant pests and diseases.
Dull autumn colour. Mild autumn nights, shade or rich soil. Colour is always strongest in cold districts on lean ground in full sun.
Frequently asked questions
Does smoke bush grow in Sydney?
Yes, in full sun and an open position, although the purple leaves fade towards green in midsummer and autumn colour is shorter than in colder districts. It performs better on the ranges and tablelands than on the humid coast.
How big does a smoke bush get?
Left unpruned, most forms reach 3 to 5 m tall and 3 to 4 m wide over about ten years. Cut back hard each winter, the same plant stays at 1.5 to 2 m.
When should I prune a smoke bush?
In late winter while it is bare. Prune lightly if you want the smoky plumes, or cut back hard to a low framework if you want larger, darker leaves on a compact plant.
Why has my smoke bush not flowered?
Plumes form only on wood at least two years old. A young plant, or one pruned hard each winter, will not produce them. Shade also reduces flowering.
Is smoke bush poisonous to dogs or cats?
It does not appear on the common lists of plants poisonous to pets, but its sap can irritate skin, so stop pets chewing the stems and wear gloves when you prune.
Ready to plant?
Choose yours from the smoke bush collection, and see the deciduous shrubs and the frost hardy plants for companions that enjoy the same conditions. Every plant is sourced from partner nurseries around Australia and delivered Australia wide.
Sources
Cotinus cultivation and pruning: Royal Horticultural Society. Plants and pets: ASPCA toxic and non-toxic plant list.
