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Freezing Seeds

Orange Beach, AL(Zone 9a)

I live in the "deep south" along Alabamas Gulf Coast. I have read in several places that a lot of seeds like to be frozen for a day or so before they are sown. Why and which ones? Will it hurt if I freeze all of my seeds before I plant them?

Everett, WA(Zone 8a)

Personally, I'd be carefull that seeds were very dry before freezing. Don't want them to burst.

Some people say that you can freeze some seeds instead of doing the conventional "cold moist" stratification. I don't know about that, I just know that "freezing moist seeds" OUGHT to kill them.

Edited to add: DUHH! Of course most seeds can take freezing. They do in every climate colder than Zone 10 or so. How do they avoid shattering from internal frost heave? I guess the seeds have their own kind o9of antifreeze.

Traditional "cold moist stratification" only needs 40 F or lower, and works OK in the fridge, not the freezer. It might need a few weeks, or up to many weeks for a few species. That needs both cool temps and moisture: a wet coffee filter in a baggie, or potting soil or vermiculite in a baggie.

This message was edited Jan 8, 2013 4:39 PM

Orange Beach, AL(Zone 9a)

interesting...about the cold moist stratification. Rick, being that you are also in a zone 8 (I find it hard to believe that washington and the beach in alabama are in the same zone) what plants/bulbs/seeds have to be, what is the word...forced (dug up and chilled to trick them into beliving that winter has come).

I have so much to learn...I miss Indiana where the tulips and crocus came up every year without fail...the only question was where would the be? (the squirrels hid them in different places)

Irving, TX(Zone 8a)

I do put some seeds for 10-14 days in the fridge (not freezer) before sowing them outdoor.
The weather is hot here in DWF and those seeds need to have a chilled time before germination.
I just put the seeds in a ceramic ramekin, cover with a paper towel and secure it with an elastic. No moisture ... that's all !
I use this technique with CILANTRO and SPINACH.
It works !!!

Everett, WA(Zone 8a)

>> (I find it hard to believe that washington and the beach in alabama are in the same zone)

The most extreme erxample of same-zone-different-climate is Zone 8 in cool, wet coastal PNW vs. hot, dry Texas.

Their spring tomato crop is burning up and dieing before my yard gets warm enoguh to even set any out! And I guess they are starting their fall tomato crop around the time my nights are getting so cold that my tomatoes turn starchy and meally.

That USDA hardiness zone is nothing more than how cold it gets in an average winter. I wish I hadf some widely-advertised measure of how warm it gets in an average summer - something like heat degree-days over 60.

Ottawa, KS(Zone 5b)


"I wish I had some widely-advertised measure of how warm it gets in an average summer..."

I think your wish may be granted in the American Horticultural Society's Heat-Zone Map:

This is a link to a small PDF version of the map

They sell a durable full-color poster version of the AHS Heat-Zone Map for $9.95, in case you wish to mount it on your wall.

Since global climate change seems to be real, our climate is a "moving target" for any map representation, whether it be a hardiness map or a heat map. Incidentally, the hardiness map has been revised, with significant differences. Based on the "old" hardiness map, I was in Zone 5b in both where we lived in south central Maine and also where we live now here in central east Kansas. It was odd that we could make such a drastic move and not change our hardiness zone. The newer hardiness map puts me in zone 6 here in the Ottawa Kansas area. You can "drag a scrubber" to compare the 1990 Department of Agriculture hardiness zone map with the 2006 National Arbor Day Foundation hardiness zone map at this webpage:

That sure looks like climate change, based on the later data. (For some perverse reason, I like to pronounce that as "later dater"). So it seems that I may be in hardiness zone 6b instead of 5b. It feels to me like climate change is real, especially since we have had a mild, almost snow-less Winter here in this area. But I do realize that we should distinguish between climate and weather. I hope that our Summer this year isn't quite so hot and humid as it was last year. Last year we had a lot of sticky uncomfortable humidity -- coupled with almost no rainfall. Oh well. I am optimistic that this year will be better.

(not associated with any product or vendor mentioned or linked)

This message was edited Feb 26, 2012 9:15 AM

Orange Beach, AL(Zone 9a)

Thanks for the link Zen! I wish that seed packets came with a heat hardiness map on it as well as a cold hardiness one. This is my first year having a large garden and I already have everything sown for the first time. I will see what works and what doesn't. Our winter this year has been mild with only a week or so of "freezing" temps at night. I think we had frost once this winter. On the flip side, last year it snowed in neighboring Pensacola. Go figure. I started seeds indoors around the new year and have just planted them out. I did direct sow with my beets, potatoes, corn and some squash. I have a 2nd round of seedlings ready to go in the ground in a couple of weeks. My tomatoes are "hardening off" which for me means putting them outside and submitting them to periods of dry rather than cold.

Does anyone have a good list of seeds/bulbs that need to be subjected to cold in order to have a better germination rate?

Everett, WA(Zone 8a)

I heard the claim that part of the half-zone chnage most areas received in the reent USDA hardiness adjustment might be due to "better data collection".

Thanks for the link to the heat-days map! When I saw "average # of days over 86F", I thought "Hmm! One or zero?". But no, I'm in a "1-7 days over 86 F" zone. I'm still guessing I'm in the low end of that range.

I think that map was designed for evaluating heat damage.

I wonder what would be the best metric for chosing tomato varieties? Number of nights that stay above 55F? Numbe of days that go above 75?

Probably no metric is as good as the experience of trying several varieties over several years and seeing which do better.

Casper, WY(Zone 4a)

Rick, choose the number of days that go above 75 for tomatoes. Above that, the nights should be above 55 anyway.

Edited to add that I have read that freezing isn't any benefit to seeds and can harm them. Best is 3 weeks in the crisper/fridge. That is what I do.

This message was edited Mar 12, 2012 9:35 PM

Orange Beach, AL(Zone 9a)

good advice...should you do that for all/most seeds, or just ones that need to be "forced"

Casper, WY(Zone 4a)

Al, just hardy perennials. Annuals don't need the cold treatment.

Everett, WA(Zone 8a)

Thanks, Blomma. That confirms my belief (and very limited experience) that I need to stick to extra-early tomato varieties adapted to realtively cool climates.

Casper, WY(Zone 4a)

Rick, try Early Girl for early tomatoes. Although in your zone 8, I wouldn't worry about. it. Big Boy is a great tomato for its large size. It is earlier than Beefsteak.

BUda, TX(Zone 8b)

FWIW, vacuum sealed all our leftover seeds from last year and stored them in the deep freeze until the middle of February and kept the bag sealed.

Beefsteak, Brandywine, Bradley Tomatoes
Okra (not sure species, dried pods from plants we grew last year)
Marketmore 76 Cucumbers
Kentucky Blue Pole Beans
Iceberg Lettuce
Organic Summer Squash Early Prolific Straightneck
Cucumber Salad Slicer
Summer Squash Burpee's Hybrid Zucchini
Cantaloupe Sierra Gold

Everything has been either started in a starter set-up or direct sown in the garden. The only seed not to have germinated at this point is the Bradley Tomato. All the seeds in the Jiffy Greenhouse were sown Sunday morning and we're looking at 85% germination or better except for the Bradley's. The seeds in the garden were sown 2 weeks ago and the squash,zucchini, and cukes are doing great.

Will get some pictures up as soon as I can find the camera...

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