Seed Banking: Preserving Genetic Diversity

Why Local Provenance Matters

Every tree population carries a genetic signature shaped by centuries of natural selection in its specific environment. An oak growing on a windswept coastal hillside has evolved differently from an oak of the same species in a sheltered inland valley, even if the two populations are only fifty kilometres apart. The coastal population carries genes for wind resistance, salt tolerance, and compact growth form. The inland population carries genes for height growth and competition in dense canopy. Plant seeds from the inland population on the coastal site and the resulting trees will struggle, snap, and die in conditions their genes never prepared them for.

This is why provenance, the geographic and ecological origin of seed, is the single most important factor in sourcing material for reforestation. Local provenance seed, collected from healthy trees growing in conditions similar to the planting site, produces seedlings already adapted to local soil chemistry, rainfall patterns, temperature extremes, frost timing, pest pressures, and disease prevalence. These adaptations are invisible but immensely valuable. They are encoded in the DNA of every seed and expressed in the physiology of every seedling that germinates from it.

Climate change complicates provenance decisions. If conditions at your site are shifting, the best-adapted genotypes may no longer be local. Some restoration programmes now practise "assisted migration," sourcing a proportion of seed from populations slightly south or downslope of the planting site, anticipating that conditions at the site will shift toward those experienced by the source population. This is a reasonable hedge, but the core principle remains: understand the conditions your trees will face and source seed from populations that have been selected by similar conditions.

Collection Ethics and Protocols

Seed collection from wild populations is a privilege that carries responsibilities. Overcollection can reduce the reproductive output of a population to the point where natural regeneration declines. The general rule is to take no more than ten to twenty percent of the available seed crop from any population in any year, and to spread collection across as many individual trees as possible, at least fifteen to twenty parent trees per species per site.

Collect only from healthy, well-formed trees that represent the characteristics you want in the restored population. Avoid collecting from isolated trees that may have been self-pollinated, as inbreeding reduces genetic fitness. Avoid trees at the edge of their range unless your planting site shares those marginal conditions. Record the location, date, species, and parent tree identity for every collection. This documentation is the seed's provenance record, and without it the seed loses much of its value because you cannot verify its origin.

Timing is critical and species-specific. Seed must be collected when fully ripe but before natural dispersal or predation by wildlife removes it. For many wind-dispersed species, the window between ripening and dispersal is only a few days. For fleshy-fruited species, collection timing must balance full ripeness against the speed at which birds consume the crop. Learn the phenology of your target species intimately. Visit potential collection trees repeatedly through the ripening period, watching for colour changes, softening of fruit, and the first signs of natural seed fall. Masanobu Fukuoka emphasised the importance of patient observation of natural cycles, and nowhere is this more relevant than in seed collection.

Drying and Storage for Long-Term Viability

Seeds fall into two broad categories for storage purposes. Orthodox seeds tolerate drying and cold storage and can remain viable for years or decades when properly processed. Recalcitrant seeds, including those of many tropical and some temperate species like oaks and chestnuts, cannot tolerate drying below a critical moisture content and lose viability rapidly once separated from the parent tree. Knowing which category your target species falls into determines your entire storage protocol.

For orthodox seeds, the process is: clean the seed by removing fruit pulp, wings, and debris; dry gradually in a well-ventilated, shaded location to a target moisture content of five to eight percent (species-specific); and store in airtight containers at one to five degrees Celsius, or at minus twenty degrees for long-term banking. Silica gel desiccant sachets inside the storage container help maintain low humidity. Properly dried and stored orthodox seeds can remain viable for five to fifty years depending on species, with some lasting much longer.

For recalcitrant seeds, immediate sowing is usually the best option. If short-term storage is necessary, keep seeds moist in damp sand or vermiculite at temperatures appropriate for the species, typically five to ten degrees for temperate species. Check regularly for fungal growth and germination, and sow as soon as conditions allow. Recalcitrant species are the most challenging to bank and the most vulnerable to loss if seed supply from wild populations is disrupted, which makes protecting their parent populations all the more important.

Community Seed Banks

Institutional seed banks, such as the Millennium Seed Bank at Kew or national gene banks, provide long-term insurance for plant genetic diversity at a global scale. But for local restoration, community seed banks are often more practical and more responsive to local needs. A community seed bank is a facility, often simple, where local people collect, process, store, and distribute seed of locally native species for restoration, agroforestry, and garden planting.

Community seed banks serve multiple functions beyond simple storage. They build local knowledge of native plant identification, phenology, and propagation. They create a social infrastructure around restoration, connecting seed collectors with planters and linking experienced practitioners with newcomers. They provide a mechanism for sharing genetic resources between landowners and restoration projects within a region. Wangari Maathai's Green Belt Movement in Kenya operated a decentralised network of community nurseries that functioned as seed banks, with local women collecting, growing, and distributing seedlings of native species adapted to their specific locality.

Establishing a community seed bank requires minimal infrastructure: a cool, dry, secure room; airtight containers; desiccant; labels; and a record-keeping system. The greatest investment is in training, teaching collectors to identify species accurately, time collection correctly, process and dry seed properly, and maintain records that preserve provenance information. Partnerships with local botanic gardens, herbaria, or experienced restoration practitioners can provide this training and ongoing quality assurance.

Connection to Climate Resilience

The genetic diversity preserved in seed banks is the raw material from which future forests will be built. Climate change is already shifting growing conditions faster than tree populations can migrate, and the species and genotypes that will thrive in fifty or a hundred years are not necessarily those that dominate today. A seed bank that captures the full genetic breadth of local tree populations, including the outlier individuals at the extremes of drought tolerance, heat tolerance, or pest resistance, preserves the adaptive potential that natural selection will draw on as conditions change.

This is not a theoretical concern. Provenance trials, long-running experiments comparing the performance of seed from different origins, consistently show that within-species genetic variation in growth, survival, and stress tolerance is enormous. Some genotypes within a population grow twice as fast as others. Some survive drought that kills ninety percent of their neighbours. This variation is the engine of adaptation, and it exists only in genetically diverse populations. A restoration project that uses seed from a single parent tree, or from a narrow geographic source, plants a genetic monoculture that may fail catastrophically when conditions shift.

Seed banking complements in situ conservation, the protection of living populations in their native habitat. Neither approach alone is sufficient. Living populations continue to evolve and adapt to changing conditions, but they can be destroyed by fire, disease, or land-use change. Seed banks preserve a snapshot of genetic diversity as insurance against such losses, but banked seed cannot evolve. The most resilient strategy combines both: protect living populations wherever possible, and bank seed from them as a backup. For pioneer species, whose rapid generation turnover means they can adapt relatively quickly, in situ conservation may be sufficient. For slow-growing climax species like native oaks or baobabs, which take decades to reach reproductive age, seed banking provides irreplaceable insurance.