For seed bank users who are interested in the practical application of our research, instructions for the User’s Guide can be download above. A few critical things to know about seed banking first:

Harrington’s Rule of Thumb: Longevity of seeds in storage approximately doubles for every 1% decrease in moisture content or every 6°C (10°F) decrease in temperature (to certain points). However,

• some seeds do not tolerate desiccation/drying,
• most seeds do not tolerate cold storage until after desiccation to appropriate levels,
• some seeds do not tolerate freezing temperatures, even with appropriate desiccation, and
• all seeds still age, even under optimal storage conditions, and will eventually lose viability.

Therefore, the most important aspects of the User’s Guide for conservation are the following, which are included in the simplified version of the User’s Guide:

• Recommended drying protocols (whether standard desiccation is tolerated or not)
• Recommended storage temperature (frozen at -18°C or refrigerated at 5°C)
• Re-Collection Intervals (RCI), or the period of time within which seeds are likely to drop below 70% of their highest recorded germination, when they should be withdrawn, used, and re-collected (or possibly regenerated through propagation) to replenish seed bank collections

For more information on recommended seed banking protocols that generally apply well to Hawaiʻi, see the Center for Plant Conservation’s CPC Best Plant Conservation Practices to Support Species Survival in the Wild. The HSBP is also in the process of developing Hawaiʻi-specific best practices and recommendations for partners.

Some important points and caveats are worth noting up front.

On seed storage behavior:

• Orthodox seeds should be frozen for long term storage (> 10 years), but they can also be desiccated and refrigerated, often for 10+ years, if short to medium term storage is your goal.
• Freeze sensitive seeds decline in frozen storage but can still be refrigerated, often for 10+ years.
• Research on seed freeze sensitivity is relatively new. Work is ongoing to better understand mechanisms and alternative storage methods. The National Laboratory for Genetic Resources Preservation reports that all tested Hawaiian species with desiccation tolerant (including orthodox or freeze sensitive) seeds survive cryopreservation in liquid nitrogen.
• We have included all Hawaiian species in this guide. For those that have not been tested, we either inferred storage behavior from congeneric/family behavior when reliable, or we stated that these categories are unknown.

On seed longevity in storage:

• Seed longevity can vary by species, population, individual plant, environmental conditions, seasonal conditions, harvest timing, and especially post-harvest handling of seeds. Thus, species with few tests may need further research. We also encourage users to follow the Hawaiʻi Rare Plant Restoration Group’s Collecting & Handling Protocols to maximize collection quality.
• At some point within the RCI, there may be a steep/fast decline of seed viability in storage. If your seeds are especially valuable, we highly recommend at least withdrawing some seeds to test for viability early in the RCI period, if not before.
• These RCI guidelines cannot replace direct testing of individual seed collections to monitor viability in storage over time.