mandolls said:I have to admit - I only tried winter sowing once, so I am not an expert. It worked really well for spinach, and for a few perennials. I only had a few tomatoes actually germinate, and they didn't sprout until May. The only reason I haven't done more of it is I really like tending them under lights. In my grow room it is "spring" in the end of February.
A friend in the Chicago area has had much better success (though I don't think she does tomatoes) - so it may work much better in zone 5.
You are right in that is doesn't matter much when they are started, at least in WI, they simply remain frozen solid until it warms up. We occasionally get an early spring, but last year winter just lasted and lasted.