Euphorbia milii, commonly known as Crown of Thorns, is a unique type of succulent, in that it has actual leaves.

The stem has long thorns, and the common name is derived from the belief that the crown of thorns worn by Jesus was made from this plant.

The better the sun exposure, the more likely to bloom.  

Allow the top inch or so of soil to dry out before watering.  Do not allow it to sit in water or become waterlogged.