[French-Connection]

Well first of all I am not sure what you winter temperatures are like, but I will give you an idea of what I have done here in France.
Seeds are sown in a tray in the house, as they need at least 60 to 67 degrees F to germinate.
Once they are up they do really need a minimum of 60, but my plants had mostly nights of 40f. This could cause poor setting on the first few trusses, but if you look at my blog my plants were ok with good setting.
Some night it went below 32 f and as long as you keep the plants free of frost they will survive.
There are ways to do this in a polytunnel as we call them. It is too exspensive to heat them the heat loss is too great. So line the lower part at least with bubble wrap. Also you can buy a mini plastic seeding green house and place the plants in this inside the polytunnel. Inside the mini greenhouse you can light a little nightlight candle on the very coldest of nights, again there is a picture on my blog from a friend that did this. Temperatures got to about 20f outside, but the plants still survived.

I built my own polytunnel, there is a fun video on my blog, but it will give you an idea. Also on my favorite links there is a good link showing details of another way to build a polytunnel.

Hope this helps.