Wood Anemone (Anemone quinquefolia)

Wood Anemone, Anemone quinquefolia

Wood Anemone, Anemone quinquefolia

Note: One white flower per plant, and leaves have 3 or 5 toothed parts, palmately arranged.

The "petals" are actually sepals; it doesn't actually have petals. The flowers supposedly close at night and when it rains. They grow in colonies. The underside of the sepals is often pink. 

This is an early spring ephemeral of woods. I find it with dogtoothed violet and spring beauty. Solitary bees like the flowers.