Let's talk proper seed storage

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Aug 30, 2008
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This was originally posted at BBay by Ohsogreen

Hello all.... Here is some info about proper seed storage, which I hope you find helpful. .
According to the National Seed Storage Lab at Ft. Collins, CO, seeds have three enemies: fresh air, moisture and heat.
The NSSL advises the moisture content most optimal for long term seed storage is is 4-8%. These moisture levels can only be obtained by slow drying seeds, over the course of 10 to 14 days (in a controlled environment).
Air drying, at room temp ( 72° F ), will only get you down to 12 - 20 % at best. At these moisture levels, freezing can harm seeds, because ice crystals can form inside them. If your seeds are only air dried at room temp, don't freeze them..
If stored at room temperatures, seeds will last perhaps 2-3 years. For each 10° F the temperature is lowered, the seed life can double (but only if the moisture content of the seed is 8 % or slightly less).
Here are the general timelines if the moisture content is proper, and they are stored in airtight containers (having a small desicant pack in with them is a smart move).

32° 50+ years

42° 25 years

52° 12 1/2 years

62° 6 years

72° 3 years

82° 1 year

90° and above-not recommended

(If your seeds are only air dried, at room temp, divide the times listed above by 2 to 2.5, to correct the average survivial / with very good germination rates (but do not freeze them).

When chosing a storage container, know that it is just as important as the moisture content & storage temp. The reason the storage container must be airtight is because fresh air carries moisture (which can lessen life, or cause false starts). It also carries oxygen, which will oxidize your seeds over time.
Your airtight storage container needs to be made of a closed cell material, such as glass, tin, or mylar for best results. Most plastics don’t work, since they are an open celled material, which air can and will penetrate over time. These include tuperware, 35mm film canisters, disposable food containers, and zip lock bags.
If you google airtight storage containers, you can find plastic ones made specifically for seed storage.
So, if you're planning on storing some special seeds for later down the road, know what the enemies are and how to eliminate them.

The requirements are basically clean, dry and not above room teimp.
To acheive this you can :
Place your seeds in a clean / new paper lunch sack, label it, and set it in a cool dry place (out of direct sun light) for several days.
Next place it in a clean / sterilized ice chest (hot water, soap, vinegar or hydrogen peroxide (not bleach), with a small Eva Dry dehumidifier (they don't require electricity to work).
Place the ice chest in an area out of direct sunlight, with a temp of 72 F or under (but above freezing), for eight days. During that eight days, (every two days) open, remove sack, shake lightly, and return promptly to the the ice chest. This will loosen any plant material still on the seeds, that you might have missed.
The next step is to place them in the final stage dryer.
You can make your own seed dryer from any of the items listed below, by cleaning / sterilizing them first (hot water, soap, vinegar or hydrogen peroxide (not bleach), then adding a small dehumidifier to it.
Refrigerator - ** non functioning, but door gasket must be in good condition
Old freezer - ** <- this is what I use.
Large dishwasher **
^^ the nice thing about all of these is, they are gasketed, have shelves, and can be had for free (curb score or recycling centers).
Place your seeds in the bottom of a clean cardboard box, or a large paper sack (wear gloves to avoid moisture & oils from your hands getting on the seeds). Place your box or sack in your clean / sterilized, gasketed, drying box.
Set the dehumidifier (*) to 70 % for two days, then drop the setting to 60 % for two days, and keep dropping it every two days, until you hit 20 %. Very few home models will dry the air to below 20 % humidity.
(*) If your dehumidifier doesn't have a digital readout, no biggie, you can buy a cheap digital temp / humidity gauge to help you slowly drop down the humidity.
After eight days, remove your seeds (wearing gloves), weight them on a scale, place them in small lots in your airtight containers, add silica desicant packs (twice the weight of the seeds you are storing), and seal your containers. Small silica desicant packs can be purchased at hobby shops, or from online packing / shipping businesses or coin dealers.
Place the small airtight containers (either numbered or with abbrevated strain names written on them in permanent marker) into a tupperware container (just to keep them together & this gives you a place to put a sheet of paper listing what is in each numbered or abbrevated containers).
I say small lots, because it makes more sense to have 20 seeds in 10 airtight containers than it does to have 200 seeds in just one.
Most people only need to pull 10 to 20 seeds at a time, and you don't want to expose all of them to air / moisture, so small lots are the way to go.
Last step, into the refrigerator........
I found this at How to Store Your Home-Grown Heirloom Seeds for Best Keeping hXXp://howtosaveseeds.com/store.php

Using Silica Gels For Final Drying

Seeds air-dried during humid weather require additional drying with desiccants such as silica gel before final storage (but don't use heat!). Most seeds benefit from drying with silica gel if they are to be stored for very long. The longest storage life for desiccation-tolerant seeds is achieved by drying them to between 5% and 7% moisture content (by weight) and then storing them at several degrees below freezing. As storage temperature rises above freezing or moisture content rises above 5 to 7%, longevity in storage goes down and the incidence of mutation rises. Seeds dried to a low moisture content with silica gel and then stored in a freezer can usually retain viability for many years.
To use silica gels for drying seeds, place equal weights of dry silica gel and seeds to be dried in a well-sealed jar for 7 to 8 days. Then transfer the dried seeds quickly into airtight storage jars and place in a freezer, refrigerator or other cool, dark place.
Carefully follow the instructions which come with your silica gels for drying them after use (to avoid burning them and rendering them useless). Silica gels suitable for drying seeds can be purchased from Southern Exposure Seed Exchange, PO Box 158, North Garden, VA 22959.
I have not stored marijuana seeds long term in the freezer (over 2 years) but I have vegtable seeds peas, watermelon etc. I dry them in the sun for a few days and then on the window sill for 10 days or so then in a zip lock bag and into the freezer. Last year I planted corn that had been saved from 1999 and got about 75% germination rate. It seems in my exp the smaller the seed the shorter the freezer life. And moisture will destroy your seeds.
The corn I planted was dried naturally in the field and stored in a zip lock bag. If the bag tears your screwed so I double bag them for safety. For Marijuana seeeds I use a pill bottle with a silica pack inside placed in a zip lock bag in the freezer.
:ciao: ozzy

Thanks for sharing

take care and be safe
Thanks for your shaing, good luck!
Hi ozzy,

I hope you don't mind me adding some more beneficial information to your excellent thread. If you would prefer it to not be here, just let me know and I will delete it and start a different thread.

I thought this information was great and will be using it in my future seed drying/storing instead of using silica gel.
After doing more reading today, I found a new product for drying seeds prior to long term storage. It is safe and non toxic vs many of the silica gels. They are called seed drying beads and are a modified ceramic which is an aluminum silicate, aka, zeolites. Being as though they are food safe, I am already sold. They are found easily from several manufactures. I found them on ebay and amazon.


peace, and pot.

Thanks Tlc :)
I have seeds that have been frozen for over 40 years now and I still get germination rates between 60% and 100%. No special drying or long list of stuff needed. I just froze bag weed seeds from about 1977 and on. Moved over a dozen times and thawed out during moves, thawed in power outages, stored in defrost and no defrost freezers. I have over 50 landrace strains... and counting. Seeds were placed into little paper envelopes and marked for content, stored in a plastic flip case box wrapped in plastic. That's it. Newer seeds I have added rice kernels to absorb any moisture. The seeds have a layer of oil on them that dries to a hard resin. That old resin has to be scratched to germinate better, but that's it. Many rags and books claim that Cannabis seeds cannot be frozen, but that is pure nonsense. They go through hard winters just fine in their native habitat with many frost and thaw cycles in the Asian stepps. And there have been many studies done (mainly in Japan) where seeds were frozen and stored for long term. In the book, Marijuana Potency where I got the idea to freeze seeds from, the author lists several studies done about freezing Cannabis seeds, and the likelihood of their lasting virtually forever when frozen. I can confirm that he was/is correct in that.

40 years and counting here. Verified by other growers in the US, Europe and Australia. Also note that I have lived on the west coast of the USA, and humidity levels are low here most of the year.
Years ago I grew some really pitiful plants in a thing called a Photon. It was like triangle shaped and used three U shaped bulbs with tint reflecting the light back into the grow. It was like 4 ft tall or maybe even shorter.

Regardless I asked the guy I got my weed from and he said he had been keeping any seeds from exceptional weed for years. I got excited and he told me to grab a hand full and he proceeded to get them. He pulled down his attic stairs, now this is in Memphis and the interior of roofs regularly hit 140, and proceeded to reach behind some fiberglass insulation for the bag of seeds. He said he had been collecting them for like 5 years.

Of the hand full I was well over 50% germination rate.....just saying they are a lot tougher than you think.

But optimally I will be keeping mine in the fridge
I keep mine in a cool dark drawer in paper or plastic containers. Never had a problem . Putting in freezer sounds interesting though. I'm guessing if I kept them in paper envelopes in a freezer bag full of rice that might just be even better. Interesting
I keep mine in a cool dark drawer in paper or plastic containers. Never had a problem . Putting in freezer sounds interesting though. I'm guessing if I kept them in paper envelopes in a freezer bag full of rice that might just be even better. Interesting
Ahh yes the freezer option. Good forever. I can see it now….Sotheby’s has a treat today as we have a freezer full of amazing genetics covering the last 60 years! Opening bid 1 million dollars do we hear 2 million!
Avoid the three things that help germination.
Heat,light,and moisture. If you do that your seeds can last for yrs.

Keep seeds dry and cool. A temperature between 32° and 41°F is ideal, so your refrigerator can be a good place to store seeds. A small amount of silica-gel desiccant added to each container will absorb moisture from the air and help keep the seeds dry.

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