Molded seeds

I saved some heirloom squash seeds and they felt dry but they molded. Are they still good or does anyone know how I can keep squash seeds from molding?

It's too late for this batch, but the way to prevent mold is to get them as dry as possible. They might need to be drier than "air-dry", but you can't use heat to dry them.


To reduce the risk of mold, humidity (relative humidity) has to be below 85%.

Depending on your house's humidity, dry squash seeds in a single layer for a few weeks. Consider prolonged drying in paper envelopes. But get them as dry as practical before bundling a pile of seeds together so that air stops circulating around each seed!

If seeds are in close contact with a paper towel or coffee filter or newspaper, you can estimate how wet they still are by examining the paper at the bottom of the pile. If it feels dry and CRISP, the seeds are fairly dry (like around 50% RH). If the paper is at all limp or does not crackle when you fl;ex it, the seeds are still WET (like over 60-70% RH).

To slow down seeds' metabolism so they stay viable more than a year or two, their RH has to be below 50%. 15% RH is ideal for long-term storage.

I suggest using silica gel (from a craft store's flower-drying isle) as a desiccant, in sealed jars, after you get seeds air-dry. Note that desiccants are only practical in sealed jars or plastic. If exposed to air, desiccants will absorb as much water as they can hold quite quickly, and then go inert.

Between 50% and 15% RH, seeds' viable lifetime DOUBLES for every 10% reduction in RH!
http://www.kew.org/sites/default/files/4_ppcont_014345_Post-harvest%20handling%20of%20seed%20collections.pdf

http://allthingsplants.com/ideas/view/RickCorey/1568/Dry-Saved-Seeds-in-Paper-Envelopes/

If you don't have a really dry climate, consider ways to use silica gel desiccants to get seeds good and dry and keep them that way!

http://allthingsplants.com/ideas/view/RickCorey/649/Silica-Gel-for-Dry-Seed-Storage/

They continue to release moisture and CO2 because seeds are alive. You can slow them down and make them last longer by keeping them VERY dry (15% - 20% RH) and cool (as low as 4 C) and dark.


If you store dried seeds in plastic Ziplocs, the moisture they continue to release as they metabolize builds up because it only diffuses slowly through plastic, and slightly faster through the "zipper".

Folding seeds into paper envelopes for long-term storage does let out any moisture they continue to release, but it means they will be as humid as your surroundings.

Inside a refrigerator is moist and humid.
The vegetable crisper drawer is the most humid part of the fridge.
Every time you open the door, more humidity condenses on seed packets.


http://allthingsplants.com/thread/view_post/517336/


Post-harvest handling of seed collections
http://www.kew.org/ucm/groups/public/documents/document/ppco...


Kew Millennium Seed Bank Project, long-term seed storage containers:
http://www.kew.org/ucm/groups/public/documents/document/ppco...

Kew: theory of desiccants and RH
http://www.kew.org/ucm/groups/public/documents/document/ppco...

Many Kew Royal Botanic Gardens Technical Information Sheets about collecting and storing seeds, written by Millennium Seed Bank staff.
http://www.kew.org/science-research-data/kew-in-depth/msbp/p...



If you have humidity around RH 50%, merely air-drying

Thanks