Evaluating Seed-banking Capacity and Propagation Potential of Endangered Sierra Bermeja Grasses: Aristida chaseae and Aristida portoricensis

Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn: <7%, Pelos del Diablo: 34%); seeds germinated at higher rates when desiccated than when fresh or desiccated and frozen. Mean time to germination was slow in both species: 86 d for fresh Pelos del Diablo and 50 d for Chase’s Threeawn. Mean germination time in Chase’s Threeawn slowed to over 90 d in drying and freezing treatments, while these treatments increased the rate of germination in Pelos del Diablo seeds. Both taxa can grow well and produce seed when grown in containers with well-drained soils; therefore, growing plants for restoration is possible. Both species’ seeds can be dried and stored at freezing temperatures, at least for the short term. The longevity of these species’ seeds held in frozen storage is unknown; thus, we advise further testing of seeds after 3, 5, and 10 y in frozen storage.