Hi;
I am 35 miles south of Tulsa, Ok. Low temp here is around minus ten, but we only get that in bad years. Zero is more ordinary. Ground is sandy, acid.
Lettuce will sprout on ice; I plant it in Feb., get it up out of the ground and it takes off when warm weather comes, gets bitter when it get hot. I plant a wide row; work the ground up fine, tamp it down with a rake, sprinkle seed on the row, then tamp it again with the rake which will cover some of the seed. Seed bought in bulk, fifty cents worth will be way more than enough of each kind. You'll have to thin rigourously. Black seeded Simpson is the best grower here. Romaine makes wonderful lettuce but is harder for me to get up. I got some head lettuce plants from a friend this year and made great heads, but they all matured at once. The leaf lettuce can stay in the ground until you want it or until it turns bitter.
Cole Crops: I have good luck with cabbage, chinese cabbage, brussels sprouts broccoli and cauliflower. To grow these in the spring you must start seeds very early and put the plants out as soon as the last frost is gone. If you do not they will not produce before it gets too hot for them. If you can plant them where they get some afternoon shade and if you will keep them watered you can nurse them thru the summer and get a second crop (of a huge first crop) in the fall. Fall plants though are better started in midsummer and allowed to mature in the fall. Fall cauliflower will sometimes get as large as a dinnerplate.
Ox