Euphorbia Milii How to grow and care Euphorbia Milii : Guide and Tips An easy to understand guide to growing and caring for a Crown of Thorns plant or Euphorbia milii. 1. Select a sunny, well-drained planting site for crown-of-thorns. Euphorbia milii will tolerate a couple of hours of shade during the hottest part of the day but does require sunshine for at least two-thirds of the day. Drainage have to be excellent or the plant will produce root rot, a fungal disease. If needed, make a raised Read more