Young stems are cloaked in fresh green foliage that provides a striking backdrop for the brilliantly colored flowers. They eventually drop as the stems mature to reveal their thorny armament (like those at the center bottom of the picture).
Crown of thorns is a bushy, very spiny, semi-succculent shrub that gets about 3 ft (1 m) in height, with a spread around 2 ft (60 cm). It has tough, leathery bright green leaves on slender fleshy stems, but the leaves often drop off on all but the youngest stems. The plant is sometimes completely leafless. The well named crown of thorns is armed with half inch (13 mm) vicious black thorns all over the stems and branches. In subtropical climates, crown of thorns bears tiny yellow-green flowers surrounded by two showy bright red bracts in spring and summer. In tropical climates, it blooms in cycles following rain throughout the year. Like the other members of the genus, Euphorbia milii oozes milky sap from bruised or broken stems and leaves. All euphorbs have a three-lobed fruit that splits apart when ripe, but crown of thorns rarely fruits in cultivation. Several named cultivars and varieties are noteworthy for their different colored bracts (pink, yellow, white, orange) and/or different growth habits. This species also has been hybridized with other euphorbs, resulting in cultivars with larger and flashier bracts.
Location Euphorbia milii is native to the island nation of Madagascar.
Crown of thorns is a slow grower that thrives on poor sandy, well drained soils, and is moderately tolerant of salt spray and salty soils. Light: Crown of thorns likes full sun, but will survive in part shade. Moisture: Although it is very tolerant of dry conditions, regular watering of crown of thorns will keep it from dropping so many leaves and coax it to bloom more. Hardiness: USDA Zones 8-11. Propagation: Grow new plants from cuttings taken in spring or summer. Dip the cut end in warm water for a few minutes to stop the bleeding, and then allow it to dry and callus over for a few days before inserting in barely damp sand. The cutting should take root in a few weeks.
The crown of thorns is planted in a commercial landscape on Miami Beach's fab Lincoln Road Mall where it makes a colorful and durable groundcover.
Crown of thorns is grown for its long lasting, colorful petal-like bracts which surround inconspicuous little flowers. Although often grown in pots on the patio, this thorny succulent is perfect for rock gardens and sunny borders. Crown of thorns is salt tolerant and often used in frostfree coastal areas, even quite near the sea. As a low growing hedge, crown of thorns makes a formidable barrier for low growing trespassers.
Features Euphorbia is a huge genus with over 2000 named species, including annuals, herbaceous perennials, shrubs, trees, and lots of cactus-like succulents, found in almost every corner of the world. If the flowers of all those species weren't so strikingly similar in anatomical structure, botanists would have split the genus into several different genera. Euphorbia flowers always have only one stigma (the female part that receives pollen) and one stamen (the male part that releases the pollen). The much adored poinsettia is a euphorb (Euphorbia pulcherrima).
Apparently all parts of most all Euphorbs are poisonous if ingested, and the milky sap can be a skin irritant.