Why is the directions not to freeze seeds so universal?

Is this like a dogma thing that just gets repeated like a mantra? I ask because being in Alaska, with winter temperatures hitting the minus 20’s F, and a frost line 4.5 feet deep, there is no seed out there that doesn’t freeze solid for the duration of the event.

Same-same for planted vs bare root. It is said that they should not freeze while an identical sibling can be sleeping away planted at -20f. Sounds to me that just avoiding temperature swings is an improvement.


I’m not your expert, but bean seeds for example are fine after being frozen for decades.
And they’re OK after being stored in a shed or outbuilding that is unheated…but I am guessing that may shorten their life vs storing in a cool dry place having a constant temperature. Corn seed, grass seed…no problems freezing.


Not clear where you read that direction. There is a world repository of seeds of edible plants in the Svalbard islands, and the place was chosen because of permafrost. They also placed the repository high enough that increases in sea level will not matter. I can attest that collard seeds in the freezer last 20+ years, chard seeds 15+ years.


I wrote a different response, but then looked up the issue, and it seems that freezers can damage seeds that haven’t been adequately dried. If you use a vacuum sealer, freezers are said to work very well for extending the life of properly dried seeds.

I once tried to germinate jalapeno pepper seeds that were from raw, fresh peppers that I chopped up, put in a freezer bag and froze. None germinated.

I guess now I know why- I had long wondered. Thanks for the question!


@Alan, i can see how there is definitely an improper way to storage them in the freezer where they dehydrate to death. Freezer burn is a thing but just because there is one specific wrong way to do it (seeds in contact with air in freezer) should not mean that all freezer storage is bad or even suspect.

I guess I’ll do some testing. I’ll divide a batch of seeds between freezer in a jar, freezer in peat moss, freezer in block of ice, and some other permutations in the lower refrigerator. Every seed is going to be different in terms of resilience but there should be a pattern where one way is gentler on seeds than another. Obviously tiny seeds are not going to be so hot lost in peat moss so even if that was the best method it would not work for them.

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I once asked a seed technologist how to store seed properly. The response was enlightening. It depends on the species.

The below information is from my own experience and reinforced by discussions with Glenn Drowns at Sandhill preservation about the best way to store different species.

Cool and dry is best followed by warm and dry. And after that, cool and damp followed by warm and damp which applies to several species. Even with optimum storage, some seed have very limited life. Onions and carrots are good examples with typical storage life under optimum conditions of about 2 years. Most common garden vegetables are best stored in a freezer properly dried with very low oxygen levels. That means a sealed glass jar with seed and desiccant will give good to very good results. What about other seed? Chestnuts, Acorns, beech seed, coconuts, and many others must never be allowed to dry out and are just fine at room temperature so long as they are moist. If they dry, they die. Pecan and walnut are best stored cool and damp in a refrigerator which prepares them to germinate.

Here are some average storage lifespans for common seed:

Beans (phaseolus Vulgaris) - 5 to 7 years with reduced germination up to 12 years
Lima Beans (Phaseolus Lunatus) - 3 to 6 years with reduced germination up to 10 years
Tepary Beans (Phaseolus Acutifolus) - 3 to 9 years, must be VERY dry
Peanuts and most other legumes are good for 3 to 5 years
Peas - 3 to 6 years, germination drops slowly over time
Cowpeas - 5 to 7 years, I’ve had decent germination with some 8 year old seed
Above best stored in a freezer after proper drying with desiccant in a sealed container

Tomatoes - 3 to 12 years, variety dependent, heart tomatoes have short storage lives
Peppers - 2 to 5 years, some varieties have short and others long storage lives
Eggplant - 2 to 7 years, most varieties will make it 4 years
Potato - 5 to 15 years, I’ve grown 10 year old potato seed with nearly 100% germination
Physalis - rarely last more than 3 years
Other solanums - species dependent, but for the most part, can be stored up to 10 years
Solanums store best in the freezer in sealed containers with desiccant. Oxygen levels should be LOW.

Field corn - up to 15 years though germination drops fast after 9 years, red varieties last longest
Sweet corn - 3 to 4 years is about the best you can get
Maize seed should be stored in the freezer after fully dried with desiccant in a sealed container.

Cucumber - 3 to 7 years, must be very dry and best in a sealed container
Cantaloupe - 4 to 9 years, very dry, sealed container, desiccant
Watermelon - 3 to 8 years, very dry, sealed container, desiccant
Squash - 2 to 6 years, very dry, sealed container
All members of the curcurbit family should be stored frozen in sealed container.

Radish, turnip, rutabage, cabbage, cauliflower, broccoli - all store best fully dry, frozen, sealed container

Carrots - Rarely last more than 2 or 3 years
Onions - 2 years is about it
Lettuce - 2 years, if kept frozen the entire time, some will germinate at 3 to 4 years
Above best stored in the freezer fully dry in a sealed container with low oxygen.

Okra - fully dry, sealed container, very low oxygen, typically good for 5 to 7 years

Glass jars in a freezer can be very fragile. I put each jar in a large ziploc bag. That way if the jar is broken, the bag keeps the seed together. I’ve only had a broken jar in the freezer one time in the last 40 years. I had to empty the freezer to get all the broken glass out. It was not that big a deal as the freezer needed to be thawed and cleaned anyway. Still makes sense to use ziploc bags as it prevents and contains glass breakage. Under no conditions should seed be left in the sun to dry. Direct sunlight is deadly to most species. The exception is a few cacti.


My chestnuts quickly rot at room temp.

Rotting is usually an indicator the seed was damaged, usually by insects. All of the beech family is tolerant of freezing in the winter and may germinate if kept at room temperature for more than 3 months. If you want them to stay viable, they must be kept moist. I store acorns and chestnuts in the refrigerator at 35 degrees in damp sphagnum moss so they will germinate rapidly in the spring. They will still rot if the seed is damaged. A rotten chestnut or pecan is one of the stinkiest smells I’ve encountered.

Thanks fusion_power, that was very informative.

And yes, every species is unique. There are tropical plants whose seed viability is measured in days. On a related note, take some varieties of bush filberts that need x number of chill hours before they will break dormancy; once they go dormant you can have them at room temperature and they will not drop dormancy until you chill therm long enough.

My mom and dad both saved seeds and their method was to dry the seeds and store in a ziplock bag inside of a mason jar in the cupboard. Always seemed to work. Not sure how scientific that is.

I have noticed that just about any seed that is in my compost pile that over winters seems to sprout. I think i could have a food forest with just my compost pile.

Here is something interesting. Squash grown from 800 year old seeds?


Good point. And, like many general rules-or-thumb, there are exceptions.
Some seeds don’t germinate if theY get dried out. Others need to be dried before freezing … but I bet some it doesn’t matter.

And Don,
Good topic, but I don’t believe it’s “universal” not to freeze…so you learn from posting incorrect info sometimes.


Cunningham’s law. The best way to get the right answer on the internet is to post the wrong answer.

There is a big difference between getting seed to germinate and getting seed to germinate and grow vigorously. I’ve grown 19 year old tomato seed and got a couple of plants from about 100 seed. The plants were seriously delayed with germination after 7 weeks and did not make a large plant for a couple of months after that. Saying this to emphasize that it is often possible to germinate very old seed, but the resulting plants may be unproductive from slow growth. Old seed often produce plants with necrotic spots on the leaves and stems. Save seed from such a plant and it is usually just as good as any fresh seed for that species.


I’m no expert on chestnuts, but I have been growing them for a couple of decades- actually 3 and harvesting nuts for 25 years. Every seed rots after a couple of weeks when left at room temp at my site, and there is no physical insect damage. Some years chestnuts get attacked by weevils here but their worms are in the nuts and very obvious.

When I did a search, it appears that molds often enter ripe nuts once they drop from the tree and that this happens within hours. I’m going to run with that theory based on my experience. Conflicting anecdotes are inevitable, but apparently, my experience is not uncommon. Nuts seem to need to be dried to store well at room temp, but drying for me is tricky because the mold comes before they dry.

Here is a pretty interesting article on storing chestnuts by the person I bought two recent trees from. His life IS chestnuts- I recommend him as a tree source- there aren’t many for grafted trees anymore.



I think we are describing different objectives Alan. I’m talking about keeping seed viable to germinate. You seem to be describing keeping chestnut seed in good condition to eat. The webpage you linked has specific statements about not over-drying chestnuts as they get hard as a rock. It also describes “sweetening” them by storing at room temperature and 60% to 70% relative humidity. Freshly harvested chestnuts (per the website) are @50% water content. I do not in any way argue that they can be kept with moisture that high. There is obviously some moisture that has to be removed before they can be stored safely. Chestnuts have to be kept moist to retain their ability to germinate. This is the same concept as with pecans and hickories where the nuts have to be dried to a specified moisture level, then chilled under high moisture to break dormancy. Chestnuts are more sensitive to over-drying than pecans. They lose the ability to germinate after about a month under dry storage conditions.

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I think I made it clear enough by quoting your statement and suggesting another opinion. I expanded on the topic because I thought his article was interesting even if it was mostly off topic-although he did mention the danger of mold entering sound nuts when stored at room temp. I like that about forums- once that original question is pretty much addressed, as you did so well here, we can expand.

I had no idea that you could make chestnuts taste sweeter by leaving them at room temp for 3 days before storage, did you? I knew it was true of apples and now I’m thinking maybe it is true of lots of species of fruits and nuts.

All that said, the problem of ripe chestnuts sometimes getting moldy at room temp is dead on topic.

Yes, I did know about sweetening chestnuts after harvest. My grandmother taught me when I was a kid. Yes, the principle applies to several species, not just fruits and nuts. Sweet potatoes are an example.

The problem with expanding, is gaining weight. :slight_smile: :smiley:

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Five native chestnut seeds planted this year…at least two dug out by squirrels I found had partial rot and squirrel had taken a bite out of the good part. So, I am not optomistic I get any germination.
The suggestion of rot or mold seems correct…as there dindn’t appear to be worm damage. I had dried the nuts and over-wintered them in the cab of my truck parked outdoors.

I do have three seedling American chestnut trees I bought as year-old seedlings, and they are doing fine.

Now that you mentioned it of sweet potatoes, I have noticed that winter squash gets sweeter in storage, but I’ve no idea how many days it is before the process stops. I let them dry out where they grow so some of the ripening must already have occured when I bring them inside, but they seem to get sweeter through fall.

I’m impressed- you are at least a 3rd generation chestnut expert.

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In all fairness a lot of the conflicting information probably comes from the simple fact that each species is different and will thrive or perish under different circumstances.


Squash sweeten over about 6 weeks. Interestingly, they sweeten most at about 55 to 60 degrees. C. Pepo does not sweeten much but it loses the latex like taste of fresh harvested fruits. C. Maxima really sweetens up in storage. C. Moschata gets better flavored but doesn’t really get sweet. C. Argyrospyra is variable with some sweetening significantly after several weeks storage.

I grew up eating chestnuts and my parents and grandparents had collected tons of wild American Chestnuts to eat. But I am not a chestnut expert and don’t have many aspirations in that direction. I do know how to germinate chestnuts and have some seedlings growing. My immediate ancestors were farmers and fruit growers. My great grandfather Noah Jones sold fruit trees throughout the southeastern U.S. driving a horse and buggy full of trees and selling them along the way. I still have the dutch oven he used when he camped out. I usually check with Castanea when I want to find out something about chestnuts.