Grow desert smoke tree in full sun on sandy ground that drains, and skip wet summer soil. Desert smoke tree is Psorothamnus spinosus, also sold as smokethorn. It is not the purple-leaf smoke bush grown for plumes.
Give it full sun, sandy soil that drains, and skip wet summer ground
| Factor | Recommended | Avoid |
|---|---|---|
| Light | Full sun, even reflected heat | Do not hide it in shade |
| Soil | Sand, gravel, or decomposed granite that drains fast | Do not plant it in clay or a hole that stays wet in summer |
| Water | Water a new plant until new growth shows, then little or none | Do not keep summer irrigation on an established plant |
| Drought | Once the roots take, let rainfall do the work | Do not soak the bed to hold a green look |
| Cold | A sheltered site for a young plant; cover it on a hard freeze | Do not plant a young plant in a frost pocket |
| Feed | Skip fertilizer | Do not add nitrogen to force growth |
| Size | About 10 to 20 feet tall and 8 to 12 feet wide | Do not crowd it against a walk you will brush |
desert smoke tree is a nearly leafless small tree with spiny, ash-gray branchlets. Give it open sun and ground that drains. Wet soil in summer is what fails it, so plant it in sand or gravel, not in a lawn that stays irrigated. [1] Water a new plant until you see new growth, then ease off. An established plant on a wash can live on rainfall. [2] Skip fertilizer. The plant is a pea-family legume on poor desert soil, and extra feed does not replace drainage.
A young plant can be hurt near 25 F, and an older one near 20 F. Site it out of a frost pocket, and cover a first-year plant if a hard freeze is coming. [3] Small gray leaves may appear for a few weeks after rain, then drop. The twigs keep working. That is how the plant looks most of the year, not a sign it died.
How much sun does desert smoke tree need?
Give it full sun. Shade makes a thin, open plant that never looks like smoke.
How often do I water an established plant?
Little or none after the first year. A deep soak in a long dry spell is enough. Wet summer soil around the roots is the usual cause of decline.
Is desert smoke tree drought tolerant?
Yes, once the roots are down. Water it while it is young, then back off. It still wants soil that drains.
Will a freeze kill a young plant?
A hard freeze near 25 F can damage a young plant. Site it out of a frost pocket, and cover it the first winter if a hard freeze is coming. Older plants hold closer to 20 F.
Plant in fall, at the old soil line, away from walks
Set a nursery can in fall, so roots work through cool weather before the first hard summer. Spring is fine if you can water. Dig a hole wider than the root ball and no deeper, and set the plant at the old soil line. Backfill with the sandy soil you dug out. Keep it off a walk, because the branch tips are spines.
- Pick a full-sun bed of sand, gravel, or decomposed granite. Keep it off irrigated lawn.
- Plant in fall, or in spring if you can water through the first dry season.
- Set the root ball even with the surrounding soil. Do not bury the stem in a rich, wet mix.
- Water until new growth shows, then skip extra summer water.
- Leave about 8 to 12 feet for the crown, and keep the spines off a path you will brush in shorts.
When should I plant desert smoke tree?
Fall is the better window, so roots work through cool weather before the first hard summer. Spring is fine if you can water through that first dry season.
How far from a walk do I plant it?
Give it about 8 to 12 feet of width, and keep the crown off a path. The branch tips are sharp.
Leave the brown inner wood — cut only a stem that hits a walk
Older inner branches turn tan and die as new silvery wood grows over them. Leave that brown wood. It is the natural form, not a missed prune. Site the plant off a walk so you do not have to cut. If one stem still hits a path, wait until the indigo flowers fade, then take that stem back to the collar and stop. Wear gloves. Do not shear it into a hedge, and do not strip the crown in one year.
- Leave brown inner wood in place.
- If a stem hits a walk, cut that stem after bloom, not a whole side of the plant.
- Wear gloves. The branch tips are spines.
- Do not shear it, and do not cut a healthy plant to the ground.
Do I prune desert smoke tree?
Usually no. Plant it off a walk, leave the brown inner wood, and cut only a stem that hits a path after the flowers fade.
Indigo flowers in late spring, then gray wood is the look
From April into June, and sometimes into July, clusters of indigo-blue pea flowers open near the branch tips. The show is short. Bees work the flowers. One-seeded pods follow. Most of the year the plant is a haze of gray twigs with almost no leaves. That smoky look is the reason for the common name, not a plume like smoke bush. If you want plants from the pods, that start is on Growing Desert Smoke Tree From Seed.
When does desert smoke tree flower?
Late spring into early summer, usually April through June. The gray, leafless look the rest of the year is normal.
Not a purple smoke bush — and not prairie clover or indigo bush
A tag that says smoke bush, purple smoke tree, or Royal Purple is usually Cotinus, a leafy shrub grown for pink or tan plumes, not this spiny desert tree — see How to Grow Smoke Bush. [4] Smoke tree on a search is almost always that shrub. Desert smoke tree is Psorothamnus: nearly leafless gray wood and indigo pea flowers.
A tag that says Dalea, prairie clover, or featherplume is a different pea-family plant, often a prairie herb or a smaller southwestern shrub — see How to Grow Prairie Clover. This plant used to be sold as Dalea spinosa. It is not that genus now.
Indigobush on a tag is often Amorpha, a wetter-bank shrub, or Baptisia false indigo in a perennial bed — see How to Grow Indigo Bush and How to Grow False Indigo. This plant is the spiny wash tree, not those.
Is this the same as smoke bush?
No. Desert smoke tree is Psorothamnus spinosus, a nearly leafless desert tree with indigo pea flowers. Smoke bush is Cotinus, grown for leafy color and plumes.
Are smoke trees hard to grow?
This desert tree is easy in full sun on sandy ground that drains, and it fails in wet summer soil. The leafy purple smoke bush is a different plant with a different water need.
What problems does smokebush have?
That question is for Cotinus smoke bush, not this plant. Desert smoke tree fails when the soil stays wet in summer, not from the usual smoke-bush leaf problems.
Do smoke trees have invasive roots?
Cotinus can sucker. Desert smoke tree makes a deep taproot in a sandy wash. Give it room, and do not plant it in a small pot as a long-term plant.
If the ground stays wet in summer and the plant looks tired, fix drainage before you add water. Next season, keep the first year watered and the soil dry once the roots take.
FAQ
Is there more than one kind of desert smoke tree?
This catalog holds one species, Psorothamnus spinosus. Nurseries sometimes sell smaller indigo bushes in the same genus. Those want the same full sun and sandy drain. They are not extra shop cards here.
Can I grow desert smoke tree in a pot?
Only as a nursery plant you plan to set in the ground. It makes a long taproot and stays stunted in a small pot. It is not a houseplant.
Can I grow it indoors?
No. It is a full-sun desert tree. Keep it outdoors on sandy ground that drains.
What can I plant near desert smoke tree?
Cactus, boulders, and other plants that stay dry in summer. Do not put a wet lawn or a shrub that needs regular irrigation under it.
Is corona de Cristo the same plant?
Some Spanish names for this tree include corona de Cristo. A houseplant sold as corona de Cristo is usually crown of thorns (Euphorbia), a succulent with milky sap — see How to Grow Euphorbia.
Can I use it as dye or medicine?
Grow it as a landscape tree, not as a dye or medicine crop. Do not cook the pods or take the plant as a remedy.
What if I see brown or pink flowers instead of indigo?
Those small flowers can be Thurber's stemsucker, a parasite that lives inside the wood. Leave them. They are not a spray job, and they are not the tree's own indigo bloom.
Related guides
Recommended plants
References
- [1] Arizona-Sonora Desert Museum -
https://www.desertmuseum.org/visit/sheets/Psospi.pdf - [2] Spadefoot Nursery -
https://www.spadefootnursery.com/trees-m-thru-z/desert-smoketree-psorothamnus-spinosus - [3] Arid Zone Trees -
https://www.aridzonetrees.com/species/psorothamnus-spinosus-smoke-tree - [4] UC Master Gardeners of Napa County -
https://ucanr.edu/blog/napa-master-gardener-column/article/smoke-bush
This note is part of Psorothamnus Guides.
More first-season notes by plant are gathered in How to Grow Guides.
Updated: Reviewed by Bosquelle Editors