Do anyone know of uncommon sessile trilliums that grow in zone 4? I already know of the most common species of trillium - mainly stemed kinds but also a few sessile. The sessile trilliums tend to confuse me with their zone hardiness as most are from central to southern Eastern United States with a few Western United State species and some Asian species. I know yellow trillium is zone 4 hardy along with a few other including Sessile and Prairie.