Crown of Thorns

Euphorbia milii

Characteristics

Culture

Crown of Thorns is winter hardy to USDA Zones 9-11 where plants are best grown in dry to medium moisture, well-drained soils in full sun. Plants react poorly to temperatures that dip below 35 degrees F. in winter. Can be grown in pots outside and brought indoors in fall.  Appreciates some midday shade in hot summer climates. Plants are tolerant of poor soils, including rocky-sandy ones. Plants are also tolerant of dry soils, but regular applications of moderate moisture may result in better bloom with less leaf drop. Wet soils, particularly in winter, can be fatal. Best located in areas with good air circulation. Indoor plants need bright light and are best grown with a gritty soil-based potting mix. Propagate from tip cuttings. Wear gloves when working with this plant. Sticky white latex sap is poisonous (avoid contact with skin, mouth or eyes).

Noteworthy Characteristics

Euphorbia milii, commonly called crown of thorns, is a woody, succulent shrub that features (a) fleshy, bright green leaves, (b) inconspicuous flowers in clusters subtended by very showy petal-like red or yellow bracts and (c) thick sharp black thorns (to 1/2″ long) which cover its water-storing branches and stems. In Madagascar, this shrub typically grows in a sprawling form to 5-6′ tall. As a houseplant, it grows at best to 2′ tall. 2 ½” bright green leaves have wedge-shaped bases. Leaves are produced on new stem growth. Inconspicuous greenish true flowers, borne in cyathia, lack both petals and sepals, but are subtended by long-lasting, colorful, petal-like, bright red or yellow bracts which are exceptionally showy. In tropical and sub-tropical locations, flowers will bloom throughout the year, but primarily in spring and summer. In Florida, flowers bloom primarily in winter and spring. House plants often bloom from late winter well into fall. Many cultivars are available in commerce.

Problems

No serious insect or disease problems. Use gloves when working with this plant. Some gardeners experience skin rashes from contact with the toxic plant sap of euphorbias. 

Garden Uses

Where winter hardy, it is an excellent selection for sunny beds, borders or rock gardens. Also useful as a low hedge or edger. Specimen. Container plant – move indoors before temperatures drop. Easy-to-grow indoor houseplant.