Fertilizing Crown of Thorns

Characteristics

• Crown of thorns is a woody succulent with a generally shrubby growth habit. It has bright green, slightly fleshy foliage and produces tiny flowers surrounded by colorful, modified leaves called bracts. Its stems are covered with extremely sharp black thorns about 1/2 inch in length. A Madagascar native, the crown of thorns can reach a mature height of 6 feet in its native habitat, but is usually only about 3 feet tall when cultivated outdoors. When grown as a potted plant indoors, it becomes about 2 feet tall after several years.

Fertilizing

• Crown of thorns is slow-growing, adding 1 foot or less to its height each year. Once it reaches its final height, the plant adds to its size by spreading out, producing more side branches and increasing the number of small, flower-producing stems. It thrives with only a single application of balanced fertilizer such as a 10-10-10 formula, diluted at the rate of 1/4 teaspoon per gallon. Feeding is best done during the plant's active growing season, in spring or summer, rather than in winter, when its growth slows and it becomes semi-dormant.

Growing Conditions

• Whether grown indoors or outdoors, a crown of thorns does best in bright sunlight for most of the day. In areas with hot summer sun, an ideal spot gets morning sun, followed by a few hours of shade in the afternoon. The plant requires well-draining soil and can do poorly or die in soil that stays wet for long periods. If your garden soil is rich in clay, add sand at planting to improve its drainage. For a potted plant, use a mixture developed for succulents, or mix 1 part peat moss, 1 part loam and 2 parts sand. Crown of thorns needs regular water while growing, but allow the soil to dry thoroughly between waterings and reduce water during winter.

Other Issues

• Crown of thorns handles drought well, but can lose leaves in extreme drought. Once watering resumes, it usually puts out new leaves. Although it needs little pruning, you can trim back stems at any time to control its size or modify its shape, but wear gloves for protection against its sharp thorns. LIke all members of the genus Euphorbia, crown of thorns has a milky white sap that can irritate the skin and cause significant damage if it gets in your eyes, so exercise care when cutting its stems.