Hi Mary. Welcome to ATP!
I agree with Caroline - putting a few seeds on a damp coffee filter will tell you about their viability. However, test seeds that germinate easily or rapidly, like many vegetables. Avoid testing difficult seeds like perennials with dormancy issues.
I think that most seeds will survive freezing if they were quite dry before freezing.
There are less common seeds that can't ever be dried (perhaps mostly tropical seeds??), but those are fairly rare. Normal, safe-to-dry seeds are sometimes called "orthodox" seeds. Gee, are there Liberal and Reform seeds? Maybe Hasidic seeds?
Seeds with dormancy requirements (usually cold-moist "stratification") are complicated.
And maybe some common seed types are even OK if they were
only fairly dry before freezing - some people have pointed out that not all seeds in nature get to be dry all winter.
Personally, when I think about ice crystals forming inside the seed embryo, I shudder and don't go down that path.
I follow advice from seed banks and try to get and keep seeds dry down to 15-30% RH, where a fairly dry house will have 30% RH. Where I live, that's like "during the winter, with the heat on".
Then after they are well and truly dry, and sealed to stay that way, big seeds banks either store seeds around 4C (just above freezing) , around -20F , or at cryogenic temps (liquid nitrogen). But dry first, for orthodox seeds.
I found this:
http://www.nsl.fs.fed.us/chapt...
"Orthodox Seeds
All orthodox seeds should be stored in moisture-proof,
sealed containers
with seed moisture contents of 5 to 10%
If the period of storage will be 3 years or less for true orthodox
species, or 2 years or less for sub-orthodox species,
temperatures of 0 to 5 °C are sufficient. For longer periods
of storage for both types of orthodox species, freezers (–18
to –20 °C) should be used.
Temperate-Recalcitrant Seeds
Temperate recalcitrant seeds should be stored with moisture
contents at least as high as that present when the mature
seeds were shed from the tree. ...
Temperatures should range from 0 to 5 °C, although 1 or 2
degrees below freezing will not harm most species.
Tropical-Recalcitrant Seeds
Storage of tropical recalcitrant seeds is done in the same
manner as storage of temperate species, except that tempera-
tures must be kept at a high level. There are differences
among species but
the lower limits are generally 12 to 20
°C. Successful storage for more than 1 year should not be
expected.
Cryogenic Storage
For long-term germplasm conservation programs, true
orthodox and sub-orthodox seeds can be dried to moisture
contents of 5 to 10% and stored in liquid nitrogen.
Germination should be retested on seedlots that will be
stored for more than 5 years. After the initial test, tests
should be carried out after 3 years and every fifth year there-
after.
Seed vigor will decline before germination percentage
(Hampton and TeKrony 1995), so tests on stored seedlots
should include some measure of vigor or germination rate
(see chapter 5). When total germination has declined 15%
from its original level, plans should be made to use the
seeds as soon as possible"
