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Plants: Species

Crown of Thorns Euphorbia milii


The crown of thorns Euphorbia milii is one of a huge family of plants known as euphorbias, which includes everything from flowering trees to branching succulents to tiny, delicate herbs. Yet despite their tremendous variety, they have similar flower structures and most produce a milky sap that is poisonous and can cause skin irritation, a form of botanical defense. In looking at crown of thorns and poinsettias Euphorbia pulcherrima you may not see the resemblance, but if you look closely, the red-colored parts on both plants are really bracts, and the true flowers are the tiny yellow bits in the middle.

Also known as spurges, euphorbias come in a variety of shapes, sizes, and areas of the world. This group of plants was named by King Juba of Mauritania after his physician, Euphorbus, who reportedly used the latex sap from one of these species in his medicinal potions. It's interesting that King Juba lived long enough to coin the name, as the sap is poisonous if swallowed and can cause irritation and blistering if it comes in contact with skin! It does have other uses, though, as a form of rubber and a drying agent for paints. In some cultures it's even used to poison the tips of arrows for hunting. Many of the euphorbia species are spectacular succulents, with beautiful flowers and ridges, lumps, and thorns that make them visually interesting, if potentially caustic, additions to a garden.