This is an interesting question that unfortunately I cannot help you with. I am planning to make some cold frames for the spring.

I know zip about growing lettuce or other cool crops. I have purchased seeds from Stokes and hope not to have wasted my money.

I have found that if you want to harvest veggies all winter long you have to start the seeds in the fall. There isn't enough light during the day to get much growth. You need longer days with stronger sunlight than what December brings. So, you could plant seeds for something like carrots that take a long time to sprout anyway and just let them do what they will or you could start some seeds indoors and then transplant them out in the cold frame after you harden them off a bit. It's always a crap shoot - if you start stuff too early and we have a mild fall you'll get too much growth and lettuce and stuff will bolt after one mild day (it seems) or you start them late and it stays cold and cloudy and nothing grows til Spring. If you have the empty space I say go ahead and plant something but don't expect a lot of winter growth.

I would try to plant some spinach or kale. What do you have to loose. They may grow slow now, but when spring comes they will have a jump on the other plants.

The link below is to a person from Nova Scotia who I heard speak at the Mother Earth News Conf and was very interesting. And she does lots of growing in cold frames.

Here is a link that might be useful: Niki Jabbour

it does depend on how the weather is for your area..
last yr i started lettuce in my cold frame in feb..and did great..it was a mild winter (temps) this winter not so.. weve been in a deep freeze since halloween..:( sigh..
i have planted lettuce in pots with cover ..against the south facing part of house..it stays toasty there..
i say you should try it.. maybe put a thermometer out in
cold frame and check it early morning..see what temps u r getting..
good luck !!!

plantman56, I followed the link and then ordered the book on indigo - thanks for the heads up. I plan on building some cold frames early early spring and need to consume as much information as possible before then.
thanks again
Lori