Seeds that in nature would need to survive a
winter outside before conditions were right for them to germinate in the
spring may require
stratification before they will sprout.
“Moist cold” stratification involves putting the seed in a damp
planting medium in a
tightly covered container (to keep them moist) and chilling in
the refrigerator at about 38-40 degrees.
With tiny seed, one way to do
this is to mix the seed with a small amount of moist
potting soil in a small
container, such as a plastic cup, that has a tight cover. After
stratification, you just plant a small amount of the seed-soil mixture
in its own pot.
Larger seed can be
folded into a damp paper towel, which is then put in a plastic
bag, tightly sealed, and placed in the refrigerator.
The length of time in the
refrigerator depends on the plant. It is important that the seed mixture
stay moist (not wet), and that the seeds be planted immediately if they
begin to germinate -– so you’ll need to check your seed every few days to
see if any have sprouted.
Two excellent guides to plant propagation
Making More Plants:
Art, and Joy of Propagation
Seed to Seed:
Seed Saving and Growing for Vegetable Gardeners