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Re: Cold stratification

TGC-The Graphics Connection wrote:
> 
> I am ready to start many of my wildflower seeds. I understand that there is
> a germination method known as "cold stratification" that promises a
> significantly greater percentage of germination than that associated with
> most other methods.
> 
> Can somebody explain the process of cold stratification to me, or point me
> in the direction of a source of this information?
> 
> Jim Klett
> 
> "Give me the luxuries of life, and I will willingly do without the necessities"
> - Frank Lloyd Wright


Hi Jim:

Some seeds have a requirement for a period of one to three months of
chilling..sometimes more.  These seeds ripen in the fall, over-winter
and germinate in the spring.
STRATIFICATION is the process of placing seeds in layers of moist media
such as sand, either in a frige or in the ground if its cold enough.

Stratification involves four things:
   Moisture
   Air
   Cold
   Time

Dehydration stops stratification, as the seeds might revert to another
dormant stage; keep 'em moist.

Oxygen in the air has a hard time getting through the seed coat. It has
a low solubility in water. But if the seed is cold, its need for O2 is
decreased and what makes it through is adequate.

Chilling temperature is the most important thing in stratification.
Try to match the cold of the local winter environment.  After the seeds
come out of dormancy, keep them chilled. Otherwise, if the COMPENSATION
TEMPERATURE is exceeded they'll go back to sleep again.

Time necessary in the cold depends on so much...the genetic components
of the seed, the conditions it developed in, the chilling requirements
of the plant from which it came...  The differences in chilling duration
can vary within a given seed lot and different lots of the same species.

Try to find the book   PLANT PROPAGATION: PRINCIPLES AND PRACTICES
                        by Hudson T. Hartman and Dale Kester
                        (Prentice Hall)

Very dry, very ponderous but stuffed with info if you want to wade
through it!  There should be a new edition out by now. (Mine is version
3...)

Good luck!

Glen Seibert
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