Crown of thorns is a Madagascan native that has traveled far since Baron Milius introduced it to France in 1821. In its homeland it reaches 5 to 6 feet, a substantial thorny shrub; in most American homes it stays under 2 feet but compensates by flowering almost continuously through the growing season. The actual flowers are tiny and inconsequential; the spectacle comes from the long-lasting bracts in red, pink, or white that cradle them, and breeders in Thailand have pushed bract size to considerable extremes.

Few houseplants are so forgiving. Crown of thorns wants bright sun, dry to medium soil, and a potting mix that drains freely. It dislikes cold wet feet and temperatures below 35 degrees Fahrenheit, which in cooler climates confines it indoors through winter. Cyclical leaf drop before the resting season is normal, if untidy. In zone 9 and warmer it can serve outdoors as a specimen, a low thorny hedge, or a rock garden plant. The sap irritates skin and eyes; the spines do the same to inattentive hands.