Temperature
60–85°F
Keep away from winter window glass and heating vents.
Crown of thorns
Euphorbia milii
Crown of thorns wants direct light and water every 10 to 21 days, once the top two inches are dry. Toxic to cats, dogs, and humans.
Light
Direct
LowMediumBright indirectDirect
A south or west window within two feet of the glass. It flowers nearly year-round given enough sun and barely at all without it.
Water
Every 10–21 days
Baseline for a 6-inch pot indoors. Check first: water when the top two inches are dry, not on a schedule.
Humidity
20% and up
Fine in normal household air. Prefers 40%.
Difficulty
Easy
Scores 2 of 5: Scores 2 of 5: drought-tolerant and long-flowering. Loses points for the spines and the caustic latex, which together make it a poor choice at child height.
Habit
Upright
Grows to 12–36 inches. No support needed.
Toxic to cats, dogs, and humans — poison severity low
Contains diterpene esters in the latex. Reported signs include skin irritation, severe eye irritation, vomiting.
If a pet has chewed a leaf, rinse the mouth with water and call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435.
Full detail for cats → Full detail for dogs →
What each authority says
- ASPCA
- No record page found under any name tested.
- NC State Extension
- Poison severity: Low · Diterpene esters in milky latex
Light
Direct light. A south or west window within two feet of the glass. It flowers nearly year-round given enough sun and barely at all without it.
Water
Every 10 to 21 days in a 6-inch pot, when the top two inches are dry.
Treat the interval as a starting point and the test as the actual instruction. Pot size, light level and season all move the number.
| Method | soak and dry |
|---|---|
| Test before watering | the top two inches are dry |
Soil and potting
Two parts cactus mix, one part perlite.
Repot roughly every 3 years, or when roots come through the drainage holes and water runs straight through without absorbing.
Common problems
Ranked by how often each turns out to be the cause for this species. Each links to a diagnosis page with the causes ranked for this species.
- Leaf drop this week
- Root rot act today
- No flowers monitor
Pest and disease guidance for this species consulted at the Missouri Botanical Garden Plant Finder, checked 2026-09-12.
Pests
Recorded for this species. Each links to identification and treatment.
- Mealybugs this week
- Spider mites act today
- Scale insects this week
Propagation
Stem cutting in soil. Roots in 21 to 42 days.
| Preferred method | stem cutting |
|---|---|
| Medium | soil |
| Time to root | 21–42 days |
| Node required | No |
| Best season | Spring and summer |
Sources
- North Carolina Extension Gardener Plant Toolbox — Euphorbia milii Checked 2026-09-12.
- Wikidata entity Q148829 — taxonomy and entity identity.
- Royal Botanic Gardens Kew, Plants of the World Online — Euphorbia milii Accepted name; family Euphorbiaceae. Checked 2026-09-12.
- Missouri Botanical Garden Plant Finder — Euphorbia milii Pest and disease guidance. Checked 2026-09-12.
- Photograph: Matt Kieffer, Wikimedia Commons , CC BY-SA 4.0.
Compiled and edited by Tony Valcarcel · 2026-09-02
Tony Valcarcel is the editor and publisher of this database, not a horticulturist
or a veterinarian. Every fact above is drawn from the sources listed, and
toxicity severity is reported only where one of them stated it.
How this is sourced.
Last updated 2026-09-02