Last year we started in the third week of March and it worked out OK. The thing that we find tricky is successive starts. If you are planning to use successive plant techniques, then you need to stagger your plant starts. Successive planting is easier from seed, but some plants need more growing time than our latitude permits.
All of that! I have been trying to get tomato and pepper seedlings started and out, stronger and faster. Plus I want to be able to put tiny plants in the ground as early as possible for those first crops like bok choi or onions.
So far I've ended up killing my seedlings because I started daytiming them outside too early (or forgot to bring them in on time, etc.) or having seedlings out in the garden that are behind those I sowed directly. I've never had to start seeds inside before living here, so maybe I just have the wrong idea about what they should look like when they go out... I figure the first thing to get right is WHEN to start them though. Got my lights and my southern facing window all ready! Our passive solar glass house will be ready to go again in March I think, depending on the snow I guess.
With the oil seed thing, I'm thinking about sunflowers. I'm reading they need 100-120 days growing season, but that they also don't take too kindly to transplanting. Does anyone know what my chances are for direct sowing sunflower, versus starting indoors? My goal is to plant a LOT more than I have indoor space to start... like 1/10 acre or so...
I have lots of volunteer sunflowers each year and end up giving some away and weeding out the others. I'd be happy to have you come and get some of mine. People have had success transplanting them. They are the multi-head type.
I should have started my onions already ;-) Cole crops soon. If you want to sell tomatoes and peppers soon, elsewise wait a bit (folks buy them too early and plant them too early). Cukes and melons much later. There a good book: http://www.amazon.com/New-Seed-Starters-Handbook/dp/0878577521 it will tell you when and what conditions for just about all your garden seeds. Oh, I have a darker cooler house too and had poor success before I got good lights and put heat to them - take the heat off once they get true leaves.