Saving the Near Extinct Harbison Hawthorn (Crataegus harbisonii): An Ex Situ Approach for Woody Plant Species Conservation

Crataegus harbisonii Beadle (Harbison’s or Harbison hawthorn) is a Tennessee (USA) endemic tree of the Rosaceae family, currently considered “critically imperiled” at the state, national, and global levels. It is known from only two extant wild locations, one in Davidson County, Tennessee consisting of a single living individual and a population of less than 100 individuals in Obion County, Tennessee. Key ex situ conservation efforts undertaken over the last three years with this critically imperiled species are reported here. The Obion County population was intensively surveyed and all C. harbisonii individuals documented. Over three seasons, seeds were collected and propagated, and clones were generated via chip-budding and grafting. Conservation seed orchards were planned and established to provide a stable, long-term source of genetically robust seed for reforestation and research. To date, 19 sources from the Obion County location as well as the single Davidson County genotype have been successfully preserved through clonal propagation, and open-pollinated seedlings produced from 12 unique mother trees. Additional material is being added annually. We report lessons learned as well as key future research directions, now enabled through the establishment of germplasm resources.