Trilliums are rhizomatous perennial herbs with a single unbranched stem and a whorl of 3 leaf-like bracts on top of stem just below the solitray flower.  The flower has 3 green sepals and 3 colored petals. The latin name of the genus 'Trillium' refers to the plants being 3-parted - 3 leaves/bracts, 3 petals, and 3 sepals.

Trilliums are divided into two major groups; pedicellate and sessile. These two groups are differentiated by whether their flower sits directly on the bracts, sessile, or whether the flower sits higher on the stem, pedicellate.