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).
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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.
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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
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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.
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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.
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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
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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.
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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.