How genetically diverse are ex situ collections of rare and endangered plant species? It is important to understand the genetic diversity held by ex situ collections and develop tools and techniques to increase this diversity wherever possible. This is important because ex situ collections that are not genetically diverse are of limited value to the long-term conservation of the species. We are working with collaborators across the country to use molecular genetics to understand how effectively the genetic diversity found in wild populations of threatened species is captured in ex situ collections. With this information, we are working with collaborators from the zoological community to understand how to effectively manage genetic diversity in ex situ collections in order to maintain genetic diversity. We are working with threatened oak species native to the southeastern United States (Quercus georgiana and Q. oglethorpensis), and critically endangered species from Hawai’i (Brighamia insignis, B. rockii, and Hibiscus waimeae ssp. hannerae). We received a National Leadership grant to support this work through 2018 (coordinated by the Montgomery Botanical Center, in collaboration with the Morton Arboretum, Brookfield Zoo, and Botanic Gardens Conservation International US), and we received funding from the Eppley Foundation to support the use of genomics to understand the diversity of all remaining Brighamia insignis plants in conservation collections. Results will be used to help conservation scientists build and manage genetically diverse ex situ collections for these and related species, and will also inform future reintroduction efforts for these species (Havens, Wood, Fant, Kramer, and outside collaborators).