Question
I was given a crown of thorns plant.  It is planted in a glass contain of sand.  I have watered it three times in five months because when I water it just a llittle the leaves turn tan or light brown and drop off or I gently pull them off.

Answer
Take it out of that glass!!!  Succulents need good drainage so put it in a pot with a good sized hole in the bottom.Cover the hole with screening  if you can get it.. I don't like crockery or rocks because they tend to block drainage. Use a potting mix of 1/2 sand or perlite and 1/2 well drained soil, slightly moistened. Gradually start to water when the soil is dry to the touch.  Euphorbia milli is a hardy plant.

For future reference, Euphorbias are winter dormant.  From Oct. to April put your plant in a very cool, dry room and don't water at all.  Al the leaves will probably fall off,no worries.  In April, start watering gradually and slowly give more and more light. If you can put it in a sunny spot for the summer and water as needed.  You should get lots of leaves and small, probably red, flowers.  This plant can grow a lot over the summer and if you need to put it in a larger pot wait till next spring.

Maureen