Technical Abstract: Ex situ conservation is required to preserve genetic diversity of the 956 species native to Hawai’i (89% endemism, 30% federally-listed as endangered or threatened). Optimizing storage procedures to maximize seed longevity is critical to the effort. Storage behavior of seeds from about 280 taxa was evaluated in parallel studies conducted in Honolulu, HI and Fort Collins, CO since 1995. Despite predictions of high incidence of recalcitrance due to the tropical location, less than 5% of the taxa produced seeds that were damaged during drying. The remaining 95% of taxa were evaluated for longevity at a range of relative humidities and storage temperatures. About 5% of the ~280 taxa studied produced seeds that aged rapidly at all temperatures studied. About 20% of the taxa produced seeds that aged rapidly when stored at -18oC, but had good storage stability when stored at 4 or 24oC. The temperature anomaly at -18oC, particularly evident in highly threatened taxa within Campanulaceae, may be avoided by storing seeds cryogenically. About 70% of the studied taxa produced seeds having characteristic orthodox behavior, though longevity varied considerably among accessions. Typical storage classifications (recalcitrant, intermediate, orthodox) do not encompass the storage trends indentified by testing the Hawaiian flora at multiple temperatures and relative humidities. Continuing research focuses on the basis of temperature anomalies and the role that storage lipids might play.