Intermediate or Recalcitrant seed
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Do not freeze or dry
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Maintain temperature and moisture from the conditions when the seed was collected
There are no perfect long-term storage solutions for recalcitrant seeds. In temperate climates, recalcitrant seed needs to be kept moist and cool (1 to 5°C) with regular air exchanges, to maintain viability for a few months up to two years (Berjak and Pammenter 2008, Hay and Probert 2011).
Some examples of Ontario species with recalcitrant seed are oaks (Quercus) and silver maple (Acer saccharinum).
If your seeds are going to be planted immediately or planted the following spring, consider placing seeds into their pre-treatment conditions described in the next section. If you are selling your seed, it is best to store seed to maintain their viability for longer periods.
Seed Storage
Orthodox seed
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Dry seed (5-12% moisture content)
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Keep cool (<5°C), refrigerator or freezer
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Store in envelopes (short term), store in plastic or glass jars (long term) if seed is dried well
Optimal, orthodox seed moisture content is typically between 5 to 12%.
For many species, seeds that have been dried can be placed in a refrigerator (temperatures between 1 to 5°C) in a breathable container such as envelopes or paper bags for 2 to 5 years. However, if you wish to store species such as willows and poplars for more than one year you will need to freeze their seed or much of it will die within a year. If you are freezing seed, it is much more important to determine the seeds moisture content to ensure seed is adequately dried.
Seed longevity
Orthodox seed will live longest when dry and cool, however some species will still not live for long.
Some examples are: willows (Salix ssp.) and the poplars (Populus ssp.), that will mostly die after only 1 month at room temperature.
Not all species can have their seed dried.
Determine the species seed storage behaviour at the seed information database (http://data.kew.org/sid/).
The majority of seed in northeastern Canada is orthodox, which means the seed can be dried and stored cool (as low as -20°C if dried very well, or in the refrigerator 1 to 5°C) to maintain its longevity.
Learn about your seeds storage behaviour
Literature cited
Berjak, P., and N. W. Pammenter. 2008. From Avicennia to Zizania: seed recalcitrance in perspective. Annals of botany 101:213–28.
Hay, F. R., and R. J. Probert. 2011. Ch. 20 - Collecting and handling seeds in the field. Pages 1–8in L. Guarino, V. Ramanatha Rao, and E. Goldberg, editors.Collecting Plant Genetic Diversity: Technical Guidelines—2011 Update. CAB International.
Fresh trembling aspen seed germinating on a moist piece of paper towel
Storage containers can include envelopes, glass jars, and even sealed plastic bags if seeds are dried below 10% moisture content.