Crown of Thorns – Crown of Thorns plants should be watered once a week when it is in a growth cycle, but only once a month while dormant. It is a succulent, and may drop leaves if the humidity changes in your house. A fast-draining medium such as cactus potting mix works best. Propagation: Take 3 inch stem cuttings in spring or summer. Dip cut ends in warm water for a few minutes to stop flow of sap then allow to dry for 24 hrs. Insert into barely moist potting mix. Will root in about 6 weeks.