Why does CPC recommend drying seeds at 25-35% RH and 25C for long term storage in the freezer?
Lisa Hill, National Laboratory for Genetic Resources Preservation, Fort Collins
Because research has shown that seeds will last best when stored at a relative humidity(RH) of 15-25% it is important to understand how the initial RH will respond to temperature changes. In this video, Lisa Hill of the National Laboratory for Genetic Resources Preservation in Fort Collins performs an experiment showing how the relative humidity in seeds changes when moved from room temperature into a freezer. She concludes that for optimal long term storage it is best to dry seeds to around 25% relative humidity before putting them into the freezer.