Seed swap
Seed swap

The Svalbard Global Seed Vault (also called the Doomsday vault) in Norway was officially opened in February 2008. During the 3 months prior to the grand opening, engineers pumped refrigerated air into the vault to bring its temperature down from a chilly -5°C to an arctic -18°C.

The Doomsday vault is designed to hold 4.5 million seed samples in perfect condition for centuries. It will eventually house almost every variety of each important food crop as an insurance policy against ecological disaster.

This is just the latest, and most high-tech, of numerous projects around the world that aim to protect and conserve our most valuable asset – the genetic diversity of plant life, and of our food crops in particular. Genetic diversity is important because it lets plant populations adapt to changing conditions, and species that can’t adapt risk extinction.

If this all sounds too much like science fiction, then rest assured that a lot of the important work of protecting genetic diversity is being done on a small scale in gardens. The easiest way to protect a plant variety is to grow it, save seeds and share those seeds with others.

To collect seeds from dry seedpods, let them mature as far as possible on the plant. If the weather turns wet just as your seedpods are reaching maturity, uproot the whole plant and hang it upside down somewhere dry. The easiest way to capture the seeds is to cover the seedpods with a paper bag and wait for them to burst open. If you have to open the dried seedpods by hand then you’ll have to separate the seeds from other plant debris before storing them.

For plants that grow fruits, leave the fruits on the plant until they’re completely ripe. You have to remove the fruit pulp, so crush the fruits up and rinse them through a sieve. If you have a lot of seeds to clean then try the fermentation method. Cover the seeds and pulp with water and leave them somewhere warm for a few days until mould starts to grow. Good seeds sink and are easily separated from the floating pulp. An added advantage of this method is that it kills some seed-borne diseases. Once you’ve separated your seeds, dry them well before storing.

For the best results, always store your seeds in a cool, dry place. Variations in temperature affect their viability, so don’t keep them in the greenhouse.

If you want your seeds to be ‘true’ – to develop into plants that are like their parents – then you need to consider whether the plants are likely to have cross-pollinated. This is more of an issue with vegetables, where you want to keep good varieties pure. Some plants are in-breeders, usually pollinating themselves and therefore easy to save seed from. Others cross-pollinate and need more care.

Some easy plants start with

  • Basil is a cross-breeder, but if you only have one variety in flower then saving seed is easy. Properly dried, basil seed lasts up to 5 years in storage.
  • French beans are self-pollinated, which makes them good for growing under cover and also for seed-savers. The only problem may be getting the seeds to dry on the plant in a wet summer – pull them up and bring them indoors before the first frosts. French bean seed stays viable for up to 3 years.
  • Nasturtiums are insect-pollinated, but very easy to collect seeds from as the large seeds fall from the plant when ripe. They’ll store for up to 5 years.
  • Tomato seeds need to have the fruit pulp removed, but tomatoes are largely self-pollinated and the seeds store for up to 5 years.

This article first appeared in Country Gardener in September 2008. I have collected together lots of links to more information on seed saving.