Crown of thorns vs African milk tree

Euphorbia milii · Euphorbia trigona

Mature size: African milk tree reaches about 96 inches; Crown of thorns tops out near 36. Buying the wrong one for a shelf means rehoming it in a year.

Why these two get mixed up

Both are Euphorbia, so they arrive on the same shelf under near-identical labels and are routinely swapped in the trade.

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

African milk tree (Euphorbia trigona) — **African milk tree** — Euphorbia trigona. Photograph by Frank Vincentz, Wikimedia Commons , CC BY-SA 3.0.

	Crown of thorns	African milk tree
Scientific name	Euphorbia milii	Euphorbia trigona
Family	Euphorbiaceae	Euphorbiaceae
Light floor	Bright indirect	Bright indirect
Water	10–21 days	14–28 days
Humidity floor	20%	20%
Mature height	12–36 in	24–96 in
Habit	upright	upright
Growth rate	moderate	moderate
Difficulty	Easy	Easy
Toxic to pets	Yes	Yes
Typical price	$12–40	$15–45

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

The differences that matter

Mature size

African milk tree reaches about 96 inches; Crown of thorns tops out near 36. Buying the wrong one for a shelf means rehoming it in a year.

Which should you buy?

In a dim room, take either — both have a bright-indirect light floor.
If you forget to water, take African milk tree, which goes 18 days between drinks.
If it is your first plant, take either — both score 2 of 5.
For a small shelf, take Crown of thorns, which stops around 36 inches.

Full entries

Crown of thorns — care fields with sources, toxicity with every authority consulted, propagation and diagnosis. African milk tree — the same.

Sources

This database's own care records for Euphorbia milii and Euphorbia trigona — every figure compared above.
Royal Botanic Gardens Kew, Plants of the World Online — accepted names and families for Euphorbia milii and Euphorbia trigona
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.