Trillium chloropetalum

The species is restricted to a relatively narrow range surrounding the San Francisco Bay Area, which includes several large cities undergoing rapid growth. Urban growth is likely to result in habitat loss and increasing fragmentation of preferred habitat. Habitat fragmentation has been shown to result in population declines in related Trillium species to the north (Jules 1998), however, Giant Trillium appears to be tolerant of habitat fragmentation and may persist in small patches of forest surrounded by grassland habitat (Case and Case 2009). Additional study is warranted to determine the impact of habitat loss on the species. Wildfire is also a pervasive threat in this area, although the specific long term impacts of fire on this species are not well understood.

Though the species is not specifically protected, it incidentally occurs in many protected areas such as, Henry W. Coe State Park, San Francisco Peninsula Watershed, Mount Diablo State Park, Mount Tamalpais Watershed, and Point Reyes National Seashore (IUCN and UNEP-WCMC 2019). Additional research on the life history, threats, and population trend of the species is needed. Given its restricted range in a rapidly urbanizing region, long-term population monitoring should be conducted. The species is known to be included in ex situ collections at a minimum of 33 botanic garden sites (BGCI 2019).