A smoke tree earns its name once a year, when its faded flower clusters stretch into thousands of fine, hairy filaments that hang over the foliage like drifting puffs of pink or smoky-gray haze. The effect can last from early summer well into fall, and few small trees or large shrubs give you that much show for so little fuss. Whether you know it as smoke tree, smoke bush, or by its botanical name Cotinus, this is one of the most forgiving ornamentals you can plant, as long as you understand a couple of quirks that trip up most gardeners.
Those quirks are worth getting straight before you dig a hole. A smoke tree wants poorer soil than you would expect, and the way you prune it decides whether you get the famous smoke at all. Get those two things right and you have a decades-long anchor for a border, a single dramatic accent, or a hard-pruned mound of vivid foliage at eye level.
What a smoke tree actually is
Smoke tree belongs to the genus Cotinus, in the Anacardiaceae, the same plant family as cashews, mangoes, and poison ivy. That family tie matters mostly because the sap can cause mild skin irritation in sensitive people, so wear gloves when you prune.
The “smoke” is not the flower. In late spring to early summer, the plant produces small, fairly plain yellow or greenish flowers in loose clusters. Most of those flowers never set seed, and as they fade their stalks elongate and grow a coat of fine hairs. It is those hairy, sterile flower stalks, massed together, that catch the light and read as smoke from across the yard.
You will run into two species, and they are not interchangeable. Cotinus coggygria, the European or Eurasian smoke bush, is the one behind nearly all the colored-leaf cultivars sold at garden centers. It is a rounded shrub, usually 10 to 15 feet tall and about as wide, prized for foliage that ranges from deep purple to gold and for heavy summer smoke. Cotinus obovatus, the American smoke tree, is native to scattered limestone soils across the southeastern and south-central United States. It grows taller, often 20 to 30 feet, carries larger blue-green leaves, and is widely considered to have the best fall color of any native tree, blazing through gold, orange, scarlet, and purple. Both are hardy in roughly USDA zones 4 or 5 through 8.
If you want a compact, colored-leaf specimen, choose a coggygria cultivar. If you want a tougher native with knockout autumn color and you have the room, plant the American species.
Where to plant a smoke tree for the best color
Plant your smoke tree in full sun. It will tolerate light or partial shade, but both the foliage color and the volume of smoke fall off noticeably without a full day of light. This is especially true of the purple-leaved varieties, which can turn muddy and greenish in shade. Aim for at least six hours of direct sun, with a little afternoon relief only in regions with punishing summer heat.
Soil is where most advice goes wrong. Smoke trees are extremely tolerant of soil type and pH, growing happily in clay, loam, or sand and in acidic, neutral, or alkaline ground. What they do not want is rich, fertile soil. In ground that is too fertile the plant grows fast and rangy, takes on a coarse look, and, more seriously, becomes far more prone to verticillium wilt, a soil fungus that can kill it within a few years. Lean, even rocky soil keeps the plant compact, bushy, and healthy. This is the rare ornamental that turns a poor, dry corner into the best-looking spot in the garden, so do not feel you need to improve the ground for it.
Good drainage is non-negotiable. Avoid low, soggy spots and anywhere near a pond or creek, where the soil stays wet. If your site is naturally damp, plant on a raised mound or slope.
How to plant a smoke tree
The best time to plant is late spring once the danger of frost has passed, or early fall in milder climates so roots can settle before winter.
Dig a hole twice as wide as the root ball and no deeper than the ball is tall, so the top of the root mass sits level with the surrounding soil. Because the plant prefers lean ground, keep soil amendment light. A modest amount of compost mixed into the backfill helps it establish, but do not load the planting hole with rich material.
Slide the plant out of its pot, tease apart any roots that have started to circle the root ball, and set it upright in the center of the hole. Backfill halfway, water to settle the soil, then finish filling and firm gently. Build a low ring of soil around the edge of the root zone to hold water, and spread a two- to three-inch layer of shredded bark or wood-chip mulch inside it, keeping the mulch a few inches clear of the trunk to prevent rot. Water it in well.
Watering and feeding without killing it
For the first year, water a newly planted smoke tree about once a week, then taper to roughly every two weeks through the second and third years. After that, an established smoke tree is genuinely drought tolerant and needs supplemental water only during prolonged dry spells. If anything, err on the dry side, because relatively dry soil gives you the best foliage and the heaviest smoke.
Resist the urge to fertilize. Because this plant actually performs best in lean soil, feeding it usually backfires, pushing soft, fast growth that looks coarse and invites verticillium wilt. In all but the poorest soils, skip fertilizer entirely. The one input worth giving is an annual spring mulch of compost, leaf mold, or well-rotted manure spread over the root zone. Mulch feeds the plant slowly and gently, holds moisture, and suppresses weeds without the harm that a bag of high-nitrogen fertilizer can do.
When and how to prune a smoke tree
Prune a smoke tree in late winter or very early spring, while it is still dormant and before the buds break. As a summer bloomer, it sets its display on growth produced earlier, so cutting at the right moment avoids removing this year’s show by mistake. Throughout the rest of the year you can safely take out any dead, diseased, or broken branches as you spot them, but save real shaping for the dormant season.
Before you make a cut, understand the trade-off, because this is the single most important thing to know about the plant. A smoke tree flowers and therefore smokes on wood that is at least a year old. Light shaping each year keeps the rangy, splayed habit in check, strengthens the limbs, and still leaves you with summer smoke. Hard pruning is a different choice entirely. Cutting all the stems back to 6 to 12 inches above the ground every late winter, a technique called coppicing, forces vigorous new shoots carrying much larger, more intensely colored leaves at eye level. The cost is that you remove all the year-old wood, so a hard-pruned plant produces little or no smoke. You are choosing between dramatic foliage and the floating haze, and you cannot maximize both in the same season. A middle path is to coppice hard only every second or third year, accepting smaller leaves but getting smoke in the off years.
For routine pruning, clean and sharpen your tools first to avoid spreading disease. Remove old, weak, crossing, or rubbing branches and any suckers, cutting back to the base or just outside the slightly swollen branch collar where a branch meets its parent. Avoid cutting into the parent wood, which opens the plant to pathogens. Thinning a few twigs from the center improves airflow. To train a single-trunk tree rather than a shrub, start young, select one strong central leader, and remove competing stems over the first few years.
Why your smoke tree is not smoking
A smoke tree that grows well but never produces its haze is the most common complaint with this plant, and the cause is almost always one of four things.
The first is hard pruning. If you coppice every year, or you cut the plant back hard to control its size, you are removing the very wood the smoke forms on. Switch to light shaping, or coppice only every few years, and the smoke returns.
The second is age. A newly planted smoke tree, or one that has just been rejuvenated by a hard cut to the ground, needs a few seasons of undisturbed old wood before it blooms heavily again. Patience usually fixes this on its own.
The third is too little sun. In shade the plant survives but flowers sparsely, and the few smoke plumes it manages are thin. Moving it, or opening up the canopy above it, restores the display.
The fourth is overly rich or wet soil. Lush conditions push leafy growth at the expense of flowering, so the plant pours its energy into foliage and skips the smoke. Stop feeding, cut back on water, and let the soil run leaner.
Solving smoke tree problems
Smoke trees are robust, and a healthy specimen in suitable conditions rarely has serious trouble. The diseases and pests below are the ones worth recognizing.
Verticillium wilt is by far the most serious threat. This soil-borne fungus enters through the roots and blocks the plant’s water-conducting tissue, causing branches to wilt, leaves to yellow and brown, and sections of the plant to die back, sometimes killing it outright. There is no cure once a plant is infected. Your defenses are preventive: keep the soil lean and well drained, avoid overfeeding, and do not plant a smoke tree where a previous wilt-susceptible plant such as a maple died. If a plant succumbs, remove and destroy it, disturb the surrounding soil as little as possible because that spreads the fungus, and do not replant another Cotinus in the same spot.
Powdery mildew shows up as a white, dusty film on the leaves, usually where air is still and humidity is high; the purple-leaved cultivars are the most prone. Improve airflow by thinning crowded growth and spacing plants properly, water at the base rather than overhead, and treat stubborn cases with a baking-soda spray or a labeled fungicide.
Insect problems are minor. Aphids cluster on new growth and leave sticky honeydew; scale and occasional leaf borers may appear. A strong jet of water, insecticidal soap, or simply encouraging ladybugs and other beneficial insects keeps these in check. Leaf spots from fungi or bacteria are mostly cosmetic and respond to good garden hygiene, including raking up fallen leaves and avoiding overhead watering.
Choosing the right smoke tree variety
The cultivar you pick sets the leaf color, the size, and how much smoke you get, so match it to the spot and the effect you want.
Royal Purple is the classic and most widely sold, a large coggygria with deep, dusky purple foliage that turns rich red in fall and reliable pink-purple smoke. Velvet Cloak is similar, with intensely dark purple leaves aging to brilliant red-orange. Grace is an open, spreading variety with red-purple new growth, soft pink-purple smoke, and superb autumn color, ideal as a focal point. Golden Spirit breaks the mold with bright golden-yellow foliage that turns fiery orange in fall and smoky-yellow plumes, perfect for lighting up a darker corner.
For smaller gardens and containers, reach for the dwarfs. Young Lady stays around 4 to 6 feet, has green leaves, and smokes heavily even when young. Winecraft Black is a compact 4- to 6-foot mound of near-black purple foliage that adapts well to a large pot. For container growing, choose a dwarf, use a wide pot with a loam-based, well-draining mix, and remember that a potted smoke tree benefits even more from a hard early-spring prune to control its size. If you have the room and want a native with the finest fall color, plant the larger American smoke tree, Cotinus obovatus, and let it grow into a 20- to 30-foot tree.
Whichever you choose, give it sun, lean soil, and a clear decision about pruning, and a smoke tree will reward you with that unmistakable summer haze and a blaze of fall color for decades. Pick your variety, find that poor, sunny corner you have been ignoring, and plant one this season.