Showcase: Crown of Thorns

According to the old Thai saying, the number of flowers on your crown of thorns will bring you luck in life. The crown of thorns (Euphorbia splendens milii) is a native of Madagascar and a cousin of the poinsettia, and was introduced to France in 1821. It is suspected it was introduced to the Middle East in ancient times and legend associates it with the crown of thorns worn by Christ. It is also known as the Christ plant or Christ thorn, and Siamese Lucky plant. This plant has gained the Royal Horticultural Society’s Award of Garden Merit.

It is a semi-succulent plant that thrives in the dry air of most homes and can tolerate occasional neglect. It is actually in the category of tropical and tender perennials. The modern varieties which are common in nurseries, grow to about 24-36 in  ( 61-91 cm). It has densely spiny stems and rich green leaves. The flowers are actually bracts, or modified leaves, fused together to form a small, circular cup. This is a plant that does well in both containers and in the garden. With a little luck the plant will bloom all year. Flowers come in pink, red, pale yellow and white. The flowers are small, up to 12 mm broad. The sap is moderately poisonous. Water regularly, do not over water. Allow the soil to dry between waterings  when it is not actively growing.

Because of its sensitivity to cold temperatures, Crown of Thorns is often cultivated as a houseplant in regions that have harsh winters. As a heat-loving species, crown of thorns performs best in sheltered areas against a south-facing wall when planted in the ground. This is particularly helpful in areas where temperatures dip below freezing in winter because the area in front of south-facing walls warms quickly during the day and radiates heat longer into the night. Avoid planting crown of thorns in shade, against north-facing walls where temperatures are slow to rise or in low points in the garden where cold air pools in winter. It will sustain significant damage below 35 F (2 C).

Climate 

The species has many cultivars and hybrids, some of which are cold hardier than others. In general, these plants grow best outdoors in U.S. Department of Agriculture hardiness zones 10a through 11, although some hybrids will survive with cold protection in zone 9. If you live in a climate that has occasional freezing temperatures, protect your plant with a thick layer of mulch before fall weather arrives, or bring it indoors before the first frost of the season.

Crown of Thorns will survive temperatures as low as 35 degrees Fahrenheit without special care. They prefer warm, dry conditions with average daytime temperatures around 80 F (26.6 C).  When daytime temperatures rise above 80 degrees, the plants need to be watered more often. In general, however, they only need water when the top inch of soil is dry to the touch. To determine your hardiness zone, the USDA plant hardiness map is on the sidebar.

Sun Exposure:

Sun to Partial Shade

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

7.6 to 7.8 (mildly alkaline)

Propagation Methods:

From softwood cuttings

Allow cut surface to callous over before planting

Seed Collecting:

Collect seed head/pod when flowers fade; allow to dry

Allow seed heads to dry on plants; remove and collect seeds