Trillium underwoodii

Habitat destruction and degradation caused by urbanization and logging present a substantial threat to related Trillium species which share Underwood’s Trillium’s range (U.S. Fish and Wildlife Service 2015). Habitat loss is expected to continue as the region encompassing the species’ range undergoes rapid human population growth. Logging presents a further threat, and negative impacts due to clear cutting have been noted in Georgia.

Overabundance of White-tailed Deer (Odocoileus virginianus) also presents a significant threat to the species. White-tailed Deer herbivory has been shown to reduce the rate of transition to reproductive adult size classes within overgrazed subpopulations of a related species with overlapping range (Leege et al. 2010). Habitat degradation caused by feral hogs (Sus domesticus) has been documented to negatively impact several species of Trillium and is likely to impact Underwood’s Trillium (Bratton 1974). Introduced species noted to impact subpopulations of related species within the region include Nepalese Browntop (Microstegium vimineum), Bush Honeysuckle (Lonicera spp.), English Ivy (Hedera helix), Chinese Privet (Ligustrum sinense), and Trifoliate Orange (Poncirus trifoliata) (U.S. Fish and Wildlife Service 2015). The magnitude of impacts from the listed threats is unknown.

Though not specifically protected throughout its range, the species incidentally occurs in several protected areas (IUCN and UNEP-WCMC 2019). The level of protection afforded at these sites may not adequately mitigate the threats to the species. Additional research is needed to determine the population size, population trend, and threats to the species.