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Re: Freezing seeds

At 11:17 PM 6/14/98 -0500, you wrote:
>Yes, seeds can be damaged, do not freeze seeds.  Seeds in nature seldom
>freeze and when they do it is a slow process.  Germination is not aided by
>freezing, 40 degrees is adequate.   It is usually a series of repeated
>cycles of cold, warm, light, dark, wet or dry for the difficult to germinate
>Midwestern seeds.  This is to insure that our irregular weather does not
>start germination at the wrong time  of year.  This enables seeds that are
>several years old to germinate at the right time of the year regardless of
>conditions.
>An informative series of books on seed germination, stratification, light,
>darkness etc. is Norm Deno's "Seed Germination Theory and Practice"
>published by the author

Freezing is not necessary for germination but how can we be sure that
germination isn't aided by freezing?  Norman Deno, in his extremely
thorough work, never subjected seeds to freezing.  Virtually all his
experiments were conducted at either 40 or 70 degrees F. 

Up here in Wisconsin seeds certainly seem to freeze in nature.  During
winter periods when there is no snow cover the soil freezes solid.  Any
seeds close enough to the surface to germinate successfully must freeze
right along with it.  It is my experience that the closer I can get to
approximating the conditions out there on the prairie the higher the
germination rate during propagation.  Freezing may not help but it
certainly can't hurt.  I would add that the National seed bank, where
germination is a priority, does some of its long term seed storage in
liquid nitrogen.  

I'm with you on the part about "rapid freezing".  Even though being frozen
doesn't hurt these northern seeds rapid freezing probably does.  Living
things that can freeze manage it by some fairly complex tricks at the
biochemical level which allow freezing without damage.  If you freeze seeds
it should be done slowly.

James MacDonald


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