Euphorbia is a very large genus of plants with more than 2,000 species. About 1,200 of them are succulents, some with bizarre shapes and wide, fleshy leaves and others that look remarkably like cacti, complete with spines. They are often grown for their architectural shapes and fascinating foliage, but a few are known for their flowers. Most Euphorbias bloom in spring or summer and go dormant in winter.