<John: Great point. The rate at which speciation occurs certainly affects the loss of winter hardiness in many plants moved around by nature. T. underwoodii could simply be speciating faster than T. lancifolium and therefore losing it's original hardiness faster. Fred Case also says that that T. underwoodii is the one of the only southern trillium species that causes problems for him in zone 4b for the reason you mention. > Tony, Even more interesting is the fact that T. underwoodii from east central Alabama comes up with the rest of the deep south sessiles in early spring, 2-3 months after the Florida panhandle forms, even though it isn't that much further north. Something strange clearly happens when things move into Florida! J.