purslanegarden said:
What about seeds inside medicine or pill bottles? ...
Those might seal a little tighter than Zip-Locs, because the jars have thicker walls and I think that screw-caps seal tighter than Zip-Loc "zippers".
I think that plenty of people never use desiccant, and can keep seeds for 5 years, but some of them are storing in paper or loosely-sealing plastic Zip-Locs. Those "breath" at least a little.
And seeds are living things, so they are still metabolizing: consuming oxygen and releasing CO2 and water.
Since the plastic container won't let humidity diffuse out through thin Zip-Loc walls and sloppy zippers, released humidity would build up over years until the inside of the jar was above 30% RH. Then the seeds would create and release water
faster, the humidity might go above 50%, and then mold could occur.
The drier they are, the slower they metabolize.
The slower they metabolize, the less water they release.
So you need to get seeds very dry before sealing them tightly for 3-5 years.
Ideally, below 30% RH. My house gets almost that dry in winter with the heat on. (So I need desiccant.)
15% RH would be even better, but don't go much lower.
You could air-dry for a few weeks, but then if your house is not pretty dry, seal them with a little desiccant for another few weeks, to get them extra-dry. If you use a lot of
fresh silica gel, use a humidity-indicating card so you can remove the silica gel if the RH gets below 15%.
I think that 3-5 years for most seeds is pretty easy if stored in paper or loose Zip-Locs.
Probably the same is true for tightly-sealing pill bottles IF you get the seeds drier than 30% RH before sealing them tightly.
But
to assure 5 years of storage with high viability, you might want to KEEP their humidity in the range of 15% - 30% RH.
That would mean something like leaving the caps loose or ajar, and storing them all inside a large tub where you keep some silica gel or other desiccant in a paper envelope or bowl. The large tub would have to seal fairly well or you'll have to replace the desiccant every month or two. If the large tub seals VERY well, you want a humidity-indicator inside the tub so you don;t dry them down below 10-15% RH and possibly hurt the seeds by getting them TOO dry.
Add darkness and cool temperatures, and you would have the exact conditions that seed collections use for LONG-term storage.
http://www.kew.org/sites/defau...
http://www.kew.org/science-con...
http://garden.org/ideas/view/R...
