Floodplain forests of the southeastern United States are species rich often with a dense and diverse liana community. Long-term trends in the density and distribution of lianas may indicate shifts in the composition of plant functional types in these forests. Liana communities in non-fragmented forests in Panama and across the Neotropics have increased in size and density over the last two decades of the 20th century. Are similar changes occurring in temperate forests? Evidence from long-term studies of liana communities in two floodplain forests in South Carolina support the findings from tropical forests. In second-growth forests of the Savannah River system data from five 1-ha plots established in 1979 and monitored for 22 years indicate a steady increase in liana size and density. Likewise in old-growth floodplain forests of the Congaree National Park liana density has increased over 12 years in six 1-ha plots after Hurricane Hugo disturbed the forests in 1989. The increase in liana density and size in these floodplain forests of the southeastern United States is of sufficient magnitude to suggest that lianas are likely influencing stand dynamics in these forests. Consequently we argue that lianas should be included in models of temperate bottomland forest development of the southeastern United States.