We talk with many people who are confused about what is the best method for keeping vegetable seed in long term storage. There is major discussion about whether seeds need oxygen, whether they should be frozen, etc. We spoke with the experts on seed storage. This is the National Seed Storage Lab in Fort Collins, Colorado.
The mission of the Seed Storage Lab is to “acquire, evaluate, preserve, and provide a national collection of genetic resources to secure the biological diversity that underpins a sustainable U.S. agricultural economy through diligent stewardship, research, and communication.”
“NSSL stores samples in conventional storage at -18° C and cryogenic storage using liquid nitrogen at -196° C (-160° C in the vapor phase). Storage method is determined by the type of seed, the size of the seed, the number of seeds in the sample, the viability of the sample, and sometimes the instructions from the donor.”
The controversy comes when people do not realize the difference between seed that has a moisture content of 8-12% and seed that has been dried down so there is no moisture in them, only the oil or lignin content. Almost all seed that is offered to the public is between 8 and 12 % moisture. There is really no controversy, only misunderstanding. If seeds have not been mechanically dried down, they should NOT be frozen, only refrigerated. They will not keep as long as seeds that have been dried to the “optimum moisture content” and then frozen. Seeds that are at the “optimum moisture content” will keep over 50 years with good germination rates when they are frozen. Different heirloom vegetable seeds require different moisture content, all are between 4 and 8 %.
NSSL says that if seed are at Optimum Moisture Content and the package is being sealed, the best gas to use in the cans would be argone. But it would be cost prohibitive and the gain would be minimal. They only use it to preserve very rare seed when they only have very few seeds.
Down to Earth Seeds dries and test all the seed before it is packaged. We make sure that all the seed is at the optimum moisture content. You simply store the cans in the freezer and you can sleep better at night knowing you have a dependable seed supply whenever the need arises.