In my usual muddled attempt at scheduling, I'm only a week or two behind.
For Zone 4b it's common to sow lettuce and broccoli some in the middle of March, peppers soon after, and tomatoes before April clears the snowy mounds left from Spring storms. First I plant them in the small circles that come with the warming mat. When they grow larger I transfer them to plastic yogurt containers or peat pots. (Some things like cucumbers, squash, or other plants that don't like being moved I start directly in a larger container with lots of space so I don't have to mess with their root system).
Similar to Kathi in Minnesota I've found that my basement is perfect for growing seedlings, but not so perfect for warm weather crops (like peppers) which need a certain temperature to sprout. My new gadget last year was a warming tray. Like a waterproof heating pad it quietly brings the temp up to a balmly 60 or 70 instead of the normal 58.
Which brings me to another Blogoversary. Last year I was starting tomatoes on my new warming mat. The year before I was tapping trees. I finished that this weekend. I have a quart of maple syrup and I'm happy. The year before that was my first year. I was suffering from snow-related Stockholm Syndrome and thinking about the Ingalls' family.
This year I'm taking walks in the woods, visiting abandoned farm buildings, making bread, and thinking about the papers I have to write.
And watching the new life springing up under the lights. First lettuce. Then parsley. Over the weekend broccoli sprang up after only a few days in the dirt. Last night I saw one lone tomato seedling raise its head.
It won't be long now. Season officially open.