What is a crown of thorns?
Crown of thorns (Euphorbia milii) is a spiny, semi-succulent shrub native to Madagascar, grown worldwide as a houseplant for its near-continuous display of small, brightly colored bracts — most often red, pink, yellow, or white — that surround tiny true flowers. Despite its common name and sharp thorns, it is not a cactus; it belongs to the spurge family (Euphorbiaceae) and is closely related to poinsettia. What makes it stand out is its staying power: given enough direct sun, it flowers almost every month of the year.
How much light does a crown of thorns need?
Crown of thorns demands direct sun — at least 3–4 hours per day, and ideally more. A south- or west-facing windowsill that gets real sunlight (not just bright sky) is the right spot. In lower light the plant survives but stops flowering, and stems become leggy and pale. If you want the colorful bracts, this plant cannot be tucked in a shaded corner.
How often should you water a crown of thorns?
Think of it like a cactus: water thoroughly, then wait for the soil to go completely dry before watering again — roughly every 2–3 weeks in the growing season. In winter, once a month is usually enough. The stems store water, so the plant easily survives a forgotten watering, but soggy soil causes root rot quickly. Always use a pot with a drainage hole and a gritty cactus or succulent mix.
How do you get a crown of thorns to bloom indoors?
The recipe is simple: more direct sun. Move it to the sunniest window in the house. Feed lightly with a balanced fertilizer diluted to half strength once in spring and once in summer. Let the soil dry between waterings. A brief cooler period in late autumn (around 55–60°F/13–15°C) can also trigger a flush of blooms — mimicking the mild dry season in its native Madagascar.
Is crown of thorns toxic to pets and people?
Yes. Like all euphorbias, crown of thorns produces a milky white latex sap that contains irritating diterpenoid esters. This sap is toxic to cats and dogs (causing drooling, vomiting, diarrhea, and skin or eye irritation), and can irritate human skin and eyes too. Always wear gloves when pruning or repotting, avoid getting sap in your eyes, and keep the plant out of reach of children and pets.
How do you prune and propagate crown of thorns?
Prune in spring or early summer to shape the plant and encourage branching — cut just above a node using gloves and eye protection to avoid the latex. Let cuttings air-dry for 24–48 hours until the cut end callouses over (the latex seals itself), then stick them into barely moist cactus mix. Keep them in a warm, bright spot and water sparingly; roots form in 4–6 weeks. One leggy plant can become several compact, well-branched pots this way.