Crown of thorns: no flowers
Why will it not flower?
On crown of thorns, the likeliest cause is not enough light. Foliage healthy but dark green and slightly stretched.
- 1Not enough light
Ranked here because it will live at bright-indirect light but needs direct to bloom.
How to tell. Foliage healthy but dark green and slightly stretched. Plenty of leaf, no bud.
What to do. Flowering costs more light than surviving does. 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.
- 2Too much nitrogen
How to tell. Lush, large, dark leaves and no buds, on a plant fed regularly with a general houseplant feed.
What to do. Stop feeding for a season, then use a lower-nitrogen feed. Nitrogen buys leaves at the expense of flowers.
- 3Not old enough
How to tell. A young plant, or one recently propagated, that has never flowered at all.
What to do. Wait. Some species take years from cutting to first bloom, and nothing brings that forward.
- 4Never given long enough nights
How to tell. A healthy plant that grows well and simply never buds, in a room where a lamp or television is on in the evening.
What to do. It needs roughly six weeks of fourteen-hour uninterrupted darkness to set buds. A spare room, or a box over it in the evenings.
Why that order, for this plant
The ranking above is not a generic list. It is computed from this species' own record — a watering interval of 10–21 days, a semi-arid origin, a humidity floor of 20%, and a light range from bright-indirect to direct. Change those figures and the order changes with them.
That is the whole point of a per-species page. No flowers on a plant watered every three days and no flowers on one watered every three weeks almost never have the same cause, and a list that ranks them identically is worth nothing to either owner. You can check the reasoning against the care fields on the species entry, which is where these numbers come from.
No percentages appear on this page. We have not run a grower survey, and a confident-sounding figure with no dataset behind it is worse than none. Order and distinguishing tests are what we can honestly give.
What Missouri Botanical Garden records
An independent authority on this species' problems, for comparison with the ladder above.
Use gloves when working with this plant. Some gardeners experience skin rashes from contact with the toxic plant sap of euphorbias. Potential disease pests include leaf spots, stem and root rots and botrytis blight. Potential insect pests include scale, mealybug and thrips. Watch for mites.
Missouri Botanical Garden Plant Finder — Euphorbia milii. Checked 2026-09-12.
Other problems recorded for this species
Also for this species
Full care entry with light, watering and soil. How to propagate it. Toxicity to cats and to dogs.
Sources
- Missouri Botanical Garden Plant Finder — Euphorbia milii Pest and disease record. Checked 2026-09-12.
- Royal Botanic Gardens Kew, Plants of the World Online — Euphorbia milii Accepted name and family. Checked 2026-09-12.
- ASPCA Animal Poison Control — Euphorbia milii Relevant if a damaged plant is being chewed rather than merely ailing.
- This database's own care record for Euphorbia milii — the watering, humidity and light figures the ranking is derived from.
Compiled and edited by Tony Valcarcel · 2026-09-12
Cause ordering is derived from this species' recorded care requirements, and the
derivation is stated above so you can disagree with it. It is not a diagnosis, and
a plant can have two problems at once. How this is sourced.