Crown – of – Thorns (Euphorbia milii) is a member of the spurge family, meaning it is related to the poinsettia along with about 2,000 other plants. The plant is a succulent, salt and drought resistant and a native of Madagascar. Being a succulent, the plant does not need much water. It has the capacity of storing water in its leaves and will stay healthy at times when watering the garden is limited due to water shortages.
The plant is a shrub that grows about 3 feet tall and 2 feet wide. It gets its name from the ½ inch long, thick black thorns that cover the stems and branches. The effect is more evident because the leaves do not last long and will drop off of all but the youngest branches.
Crown-of-Thorns will bloom differently, depending on whether it is in a sub-tropical or tropical environment. In the sub-tropics, you will get small, yellow-green flowers in the spring and summer. In the tropical regions, it will bloom all year, but only after a rain storm.
Crown-of-Thorns is a tough plant that loves poor, sandy, well-drained soils. It prefers a full sun situation, but can take partial shade. Moisture has a big effect on the plant. While it does very well in dry conditions, giving it a regular watering will help the leaves stay on the plant longer. It loses its leaves so that the plant can conserve water and use the water it has just for the important parts. The plant is hardy in USDA zones 8 to 11.
Use the plant in a rock garden or as a border plant. It also does well in container on patios or decks. Plant it as a hedge and very few will try and walk through it.
Crown-of-Thorns has very few problems. It can be bothered by scale insects, mealybugs, spider mites and thrips, but other insects mostly leave it alone. Diseases are something you have to worry about more, but most of them can be prevented by making sure the soil is well drained and bottom watering, keeping the leaves as dry as possible. Remove any dead leaves and keep the area free from fallen debris to minimize the chance of a fungal disease having a place to grow and reproduce. Be on the look out for bacterial and fungal leaf spots, fusarium and rhizoctonia stem and root rots and botrytis flower blight.
Scientists are constantly cross breading different varieties of Crown of Thorns in order to make a better, more disease and to develop certain traits. For instancRosalie, Vulcanus and Saturnus have thicker stems, Short and Sweet is a dwarf variety with soft spines and dark green leaves. Mini-Bell is similar, but it has a more compact growth. Jingle Bells has soft pink flowers with red and green accents. Spring Song is a light creamy yellow. Summer Song is rich, creamy yellow with and emerald green spot at the center.
University of Florida