Crown of thorns vs Zebra haworthia

Euphorbia milii · Haworthiopsis attenuata

Pet safety: Zebra haworthia is listed non-toxic to cats and dogs; Crown of thorns is toxic (diterpene esters in the latex).

Why these two get mixed up

Zebra haworthia is recorded here as a pet-safe alternative to Crown of thorns, so the question is usually whether the swap is actually a fair one.

Crown of thorns (Euphorbia milii) — **Crown of thorns** — Euphorbia milii. Photograph by Matt Kieffer, Wikimedia Commons , CC BY-SA 4.0.

Zebra haworthia (Haworthiopsis attenuata) — **Zebra haworthia** — Haworthiopsis attenuata. Photograph by Wikimedia Commons contributor, Wikimedia Commons , CC BY-SA 3.0.

	Crown of thorns	Zebra haworthia
Scientific name	Euphorbia milii	Haworthiopsis attenuata
Family	Euphorbiaceae	Asphodelaceae
Light floor	Bright indirect	Medium
Water	10–21 days	14–24 days
Humidity floor	20%	20%
Mature height	12–36 in	4–8 in
Habit	upright	rosette
Growth rate	moderate	slow
Difficulty	Easy	Easy
Toxic to pets	Yes	No
Typical price	$12–40	$8–25

Highlighted cells are where the two actually differ. Everything else they share.

The differences that matter

Pet safety

This is the difference that matters most. Zebra haworthia is listed non-toxic to cats and dogs; Crown of thorns is toxic (diterpene esters in the latex). If the two are sold under the same name, a mislabelled plant is a genuine risk in a house with animals.

Mature size

Crown of thorns reaches about 36 inches; Zebra haworthia tops out near 8. Buying the wrong one for a shelf means rehoming it in a year.

Light

Zebra haworthia tolerates medium light; Crown of thorns needs bright-indirect as a floor. Put the second in the first's spot and it stretches and declines.

Habit

Crown of thorns grows upright; Zebra haworthia grows rosette. That decides where each one physically works.

Not even related

Crown of thorns is Euphorbiaceae, Zebra haworthia is Asphodelaceae. They share a shop label and nothing else — different families, different continents, different care.

Which should you buy?

With a cat or dog in the house, take Zebra haworthia. The other is toxic, and if the shop label is wrong you will not know which you have brought home.
In a dim room, take Zebra haworthia.
If you forget to water, take Zebra haworthia, which goes 18 days between drinks.
If it is your first plant, take Zebra haworthia, at 1 of 5.
For a small shelf, take Zebra haworthia, which stops around 8 inches.

Full entries

Crown of thorns — care fields with sources, toxicity with every authority consulted, propagation and diagnosis. Zebra haworthia — the same.

Sources

This database's own care records for Euphorbia milii and Haworthiopsis attenuata — every figure compared above.
Royal Botanic Gardens Kew, Plants of the World Online — accepted names and families for Euphorbia milii and Haworthiopsis attenuata
ASPCA Animal Poison Control — toxicity classification for both, cited on each species entry
Photographs: Wikimedia Commons, individually credited and licensed above

Compiled and edited by Tony Valcarcel · 2026-09-12
Every comparison above is drawn from a recorded field. Where the honest distinguisher is visual we show both photographs rather than describing a leaf we have no field for. How this is sourced.