Euphorbia milii or Crown-of-Thorns is a woody, spiny, climbing shrub native to Madagascar. Stems will reach up to 4 feet (1.2 m) in length with many spines. Stems are slender from 1/8 to 3/8 inches (0.5-0.95 cm) thick. Spines are ~0.2 inches (0.5 cm) long and 1/8 inches (0.3 cm) thick at the base. Leaves are truncate at the apex, light to dark green, growing to 1.5 inches (3.8-5.1 cm) long. Leaves are usually gathered near the stem or at branch ends. There are many varieties and hybrids in existence today. They all vary in form, size and in bract color. They are very easy plants to grow and are hardy in the landscape in USDA zones 10-11. This plant is considered poisonous and should be kept away from small children and animals.
Blooming: Plants will bloom the whole year round. Cymes are long peduncled, with the cyathia subtended by two bright red bracts. Hybrids vary in color from orange, yellow to pink.
Culture: Euphorbia milii needs full sun to partial shade with a well-drained soil mix. In the greenhouse, we use a soil mix consisting of 1 part peat moss to 1 part loam to 2 parts sand. The plants are well watered and allowed to dry thoroughly before watering again. We fertilize the plants only once during the season with a balanced fertilizer. The plants tend to grow a little faster if given regular watering, but care should be taken not to keep them too wet. Plants can become temporarily deciduous when in stress or severe drought. During the winter months in the greenhouse, water is restricted to only enough to keep the foliage from dropping.
Propagation: Euphorbia milii is propagated using stem cuttings and from seed when available. Stem cuttings need to dry about one week before the rooting process can begin. Cut ends will leak milky sap; this can be overcome by dipping cut ends in charcoal dust.
Euphorbia milii was featured as Plant of the Week September 25-October 1, 2009.
Guide to Past Plants-of-the-Week:
Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.