If I work with a species that has recalcitrant seeds and cannot be stored in a seed bank, are there any other options besides propagating all seeds right after they are collected?

Sometimes, it may be possible to store recalcitrant seeds for a short period of time. This might mean keeping the seeds inside the fruits, so they do not dry out, and storing them in a protected/shaded location in humid conditions. However, it may not work for some species, or might only work for a few days. If you have abundant seeds, you could test this by trial and error, but we recommend checking for any local resources or expertise first. There may be botanical gardens, universities, or other restoration projects in your country or region where people have experience with your species. The Seed Conservation Directory of Expertise is another place to search for experts in your region.

For common native species that have recalcitrant seeds, an alternative to seed banking is seed production areas (SPAs, please click here for further details). They can also be used together with seed banking for species with orthodox seeds that are difficult to collect in the wild. In the context of ecological restoration, SPAs are managed plantings of wild-sourced plants for the specific purpose of increasing the number of seeds available for restoration. They can range from small seed beds managed by one organization to large networks of SPAs under government or commercial management. SPAs can focus on one species or contain a mixture of species. If you face challenges with seed sourcing or seed banking, establishing an SPA (or connecting to an existing SPA network) might be a useful option. However, it is important to distinguish an SPA for restoration from SPAs for agricultural or other commercial purposes, which may focus on traits such as minimizing dormancy (speeding germination) or synchronizing germination (so that seeds germinate at the same time). While these traits make it easier to grow plants, this eliminates a lot of natural genetic diversity found in wild plants, which ultimately causes the plants to be poorly adapted to natural conditions in restoration sites. In addition, even restoration-focused SPAs face risks to genetic diversity resulting from cultivation, so it is critical to plan and manage SPAs carefully. To learn more, we recommend the articles “Seed production areas for the global restoration challenge” (Nevill et al. 2016) and “Seed production areas are crucial to conservation outcomes: benefits and risks of an emerging restoration tool” (Zinnen et al. 2021).

For rare, endangered, and endemic species conservation, there are high-tech options such as cryopreservation and micropropagation. Cryopreservation uses liquid nitrogen to quickly freeze seeds (or embryos, other tissue samples of plants, or even animal cells or tissues) to extremely low temperatures, usually below -140°C. There is promising research that shows cryopreservation can be an effective method for storing some recalcitrant seeds or embryos, but it requires specialized equipment and knowledge. Micropropagation uses a sterile environment to grow plants in vitro — under glass, such as in test tubes — and can include tissue culture, where plants are grown from seeds, embryos, or even other plant tissue. It works well for many species, but it requires a specialized laboratory, and growing protocols often need to be fine-tuned for each individual species. Both methods have some limitations and will not work for all species with recalcitrant seeds. The Center for Plant Conservation is a great place to learn more about these methods.