Improving the storability of seeds
The best time to collect seeds is at natural dispersal when they will have ripened and reached maximum storage potential. However, if seed collectors have been forced to collect seeds that are not fully mature, drying them immediately under normal seed bank drying conditions will reduce their storage life or, in the case of very immature seeds, kill them.
Sansevieria sp. The immature green fruits gradually turn orange if left to ripen after collection.
Research at the MSB has shown that, under appropriate conditions, immature collections will continue to develop and reach maximum storage potential. Seeds are best left attached to the plant or in pods, capsules, fruits or berries under similar conditions to those they would have experienced naturally on the plant. Immature seeds received at the MSB are spread out on trays in temperature and humidity controlled rooms or cabinets, which mimic the environment from where they came. This post-harvest ripening is best performed immediately after harvest.
Research on Solanum dulcamara L. (Woody Nightshade) revealed that immature seeds in unripe fruits continued to develop after harvest if left in a cool and humid environment for 21 days. Fruits processed as soon as they ripened and turned red produced high quality seed but seeds left unprocessed in ripe fruits began to age prematurely.
Our research on Solanum dulcamara has also shown that seeds extracted from fleshy fruits benefit from a few days of slow drying under ambient conditions before being transferred to the seed bank dry room where they dry rapidly.
Key findings:
- Immature collections can be successfully ripened, maximising seed storage potential, and ensuring that the high cost of collecting is not wasted.
- Seeds must not be too damp (less than 80%eRH) otherwise moulds will develop.
- To prevent deterioration by ageing, seeds must be removed and dried as soon as fruits are ripe.
Further information:
Technical information sheet: Post-harvest handling of seed collections
Hay, FR, Probert, RJ and Coomber, SA (1997). Development of dessication tolerance and longevity in seeds from detached capsules of foxglove (Digitalis pupurea L.) Annals of Botany 79: 419-427.
Hay, FR and Smith, RD (2003). Seed maturity: when to collect seeds from wild plants, pp. 97-133. In: RD Smith, JD Dickie. SH. Linington, HW Pritchard &. R.J Probert (eds) Seed conservation: turning science into practice. Royal Botanic Gardens, Kew, UK.