Hi, Kim! Welcome to NGA. I like your screen name!
Big seeds with hard, thick coats often need to be scratched and soaked, just so the water REACHES the embryo!
Do
any annual seeds need stratification or varying temperatures? Or only perennials?
If you're talking about vegetables, they tend to be easy or at least simple: either all they need is moisture, or that plus a little warmth. (Or in the case of lettuce - moisture and COOL soil.)
I often go to Tom Clothier to find a suggestion for hard-to-germinate seeds. But you need to know the "Latin name", and sometimes need to know more than one Latin synonym, since those darn taxonomists keep changing names to protect the innocent.
He also has a nice article about ideal seed germination temperatures: what makes them germinate fastest may not be the conditions that make the MOST of them germinate.
http://tomclothier.hort.net/
P.S. I don't do winter-sowing myself, but they will be quick to tell you that "stratification" is best done in a milk jug, on the back porch all winter, and then just shovel the sprouted seedlings into your garden.
