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Crown of thorns (Euphorbia milii) care

Succulents & cacti · easy to keep

Last updated

Crown of thorns (Euphorbia milii) wants bright light with direct sun. Water it every 10 days. Water when the top half of the pot is dry. It is a leafy shrub, not a cactus, and drops leaves if left dry too long; water less in winter. Pot it in gritty cactus compost, at least half grit or perlite. A weak cactus feed two or three times over the summer, and repot every 2 years. Humidity: indifferent; dry air is ideal. Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house.

Crown of thorns: woody, viciously spiny stems with fresh green leaves at the tips and small red, pink or yellow bracts that it carries for much of the year. It takes more water than a cactus, and drops its leaves when it is too dry or too cold — then grows them back.

Quick facts

Water
Water every 10 days. Water when the top half of the pot is dry. It is a leafy shrub, not a cactus, and drops leaves if left dry too long; water less in winter.
Light
Bright light with direct sun.
Humidity
Indifferent; dry air is ideal.
Soil
Gritty cactus compost, at least half grit or perlite.
Feeding
A weak cactus feed two or three times over the summer.
Repotting
Repot every 2 years.
Toxic to pets
Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house. The white latex burns skin and can cause lasting damage to eyes — wear gloves and eye protection when cutting one, and wash immediately if it touches you. The ASPCA does not list Euphorbia milii itself, but lists a relative, Pencil Cactus (Euphorbia tirucalli), as toxic to cats and dogs (checked 26 October 2026).
Difficulty
Easy.
Mature size
50–90 cm indoors.
Native to
Madagascar.

Watering a Crown of thorns

Water every 10 days. Water when the top half of the pot is dry. It is a leafy shrub, not a cactus, and drops leaves if left dry too long; water less in winter.

That cadence is the one PlantParlour sets for this species when you name it, and it is deliberately on the cautious side — a plant that asks a day early is safer than one that asks a day late. Log each watering and the reminder moves with the plant rather than with the calendar.

Light

As much direct sun as you can give it — four to six hours minimum. An echeveria in a normal room stretches into a pale tower within weeks, and no amount of later light will make it compact again.

Humidity and temperature

Indifferent; dry air is ideal. Central heating in winter is what turns a comfortable room into a dry one, and it is the usual reason an established plant suddenly browns at the edges or picks up spider mites.

Soil and potting

Cactus compost cut with more grit. A terracotta pot helps because it wicks water out of the mix and away from the roots.

Feeding

A weak cactus feed two or three times over the summer. Stop feeding in autumn and start again when you see new growth in spring — feeding a plant that isn't growing just builds up salts in the pot.

Repotting

Repot every 2 years. Every two or three years in spring, into a pot barely larger than the rosette.

Common problems

Propagation

Stem cuttings, wearing gloves. Dip the cut end in water to stop the latex, let it callus for several days, then root in dry gritty mix.

A cutting taken in PlantParlour keeps its link to the plant it came from, so a propagation years later still traces back to the mother plant — which is the point if you ever sell or trade it.

Toxicity and safety

Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house. The white latex burns skin and can cause lasting damage to eyes — wear gloves and eye protection when cutting one, and wash immediately if it touches you.

The ASPCA does not list Euphorbia milii itself, but lists a relative, Pencil Cactus (Euphorbia tirucalli), as toxic to cats and dogs (checked 26 October 2026).

If your pet has eaten a plant, call your vet, the ASPCA Animal Poison Control Center on (888) 426-4435, or the Pet Poison Helpline on (855) 764-7661. Both are open around the clock and may charge a consultation fee. Take the plant or its label with you.

This is general information, not veterinary advice. We don't test plants: what we say about toxicity follows the ASPCA's published plant list as it stood on 26 October 2026, and that list can change. "Non-toxic" means not poisonous — a pet that eats enough of any plant can still vomit, and fertiliser, pesticide or leaf shine on a plant can harm it. It also only helps if the plant is what you think it is. It covers cats and dogs only; ask your vet about rabbits, birds, reptiles or anything else, and a doctor about children. Read our terms.

Every houseplant in the library the ASPCA lists as non-toxic to cats and dogs

Questions people ask

How often should you water a Crown of thorns?

Water every 10 days as a starting point — that is the cadence PlantParlour sets for Euphorbia milii. Water when the top half of the pot is dry. It is a leafy shrub, not a cactus, and drops leaves if left dry too long; water less in winter. Light, pot size and the time of year all move that number, so treat it as a reminder to go and check rather than a rule.

How much light does a Crown of thorns need?

As much direct sun as you can give it — four to six hours minimum. An echeveria in a normal room stretches into a pale tower within weeks, and no amount of later light will make it compact again.

Is Crown of thorns toxic to cats and dogs?

Toxic to cats, dogs and people, and the most genuinely hazardous plant in the house. The white latex burns skin and can cause lasting damage to eyes — wear gloves and eye protection when cutting one, and wash immediately if it touches you. The ASPCA does not list Euphorbia milii itself, but lists a relative, Pencil Cactus (Euphorbia tirucalli), as toxic to cats and dogs (checked 26 October 2026). If a pet has eaten part of a plant, call your vet or the ASPCA Animal Poison Control Center on (888) 426-4435 straight away.

How do you propagate a Crown of thorns?

Stem cuttings, wearing gloves. Dip the cut end in water to stop the latex, let it callus for several days, then root in dry gritty mix.

Or browse every plant in the library.

Keep this plant's record

PlantParlour gives your Crown of thorns its own page: a photo timeline, reminders set to the cadences above, and every watering, feed, repot and problem written down. Trade or sell it and the whole history goes with it.

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