A popular import from Madagascar, crown of thorns can bloom year-round if given enough light. Long, spoon-shape leaves appear at the ends of spiky branches, along with clusters of tiny flowers. You might not notice the flowers because they're so small, but you will see the red, salmon, or yellow bracts that surround them.
When the plant is in bloom, allow only the top inch or so of soil to dry out between watering. When the plant is not blooming, be sure the top half of the pot's soil is dry before watering. Don't let the entire pot dry out, however, or the plant will drop its leaves. If your plant dries out and loses its leaves, it will grow new ones in a few weeks after you begin watering.
Direct sun produces the best bloom, but crown of thorns adapts to medium light. Fertilize three times in summer using a bloom-booster fertilizer of 10-30-10.