ZOne 4 second planting

I am in MN zone 4. Realistically, what can I actually plant to get two crops out of a "square"? We have such a short growing season. Anyone want to share what has worked for them? In my regular garden, when something was done for the summer I never replanted anything else.

I'm curious to hear what people have to say as well, since I'm in the same boat.

This is my first gardening attempt, but I am experimenting with this a bit. I've got two boxes. One of them has peas (I really like peas, and I've got a couple different kinds). Once the peas are out in the summer, I'll try to get a fall crop of radishes, lettuce, spinach, etc. going and see how long it lasts before winter sets in -- at the very least, I'm going to grow kale, which apparently does very well in cold weather.

My other box is mainly for summer crops -- tomatoes, peppers, beans, and the like. I don't know if I'll be able to get a fall crop out of that box, but I've planted a spring crop in it. I've got some radishes, since they'll be out by the time I need to put the summer crops in, and then most of the rest of the box is leaf lettuce/mesclun mix. I planted a lot of squares, and my hope is to harvest some "micro-greens" for a week or two before I have to tear the lettuce out to make room for the summer stuff. The seeds don't cost much, so I figured I'd see what I could get in a short time!

We'll see how my garden works out, but I think two plantings is definitely doable: short spring/summer or longer spring/fall. Three plantings would probably involve a lot of "extending the season" tricks. Maybe next year.

We have a really short growing season here too. I found radishes could be planted a few times in sequence. If the first batch of lettuce is planted early, another can be put in after its done. Early spinach followed by lettuce or carrots worked, the carrots were smallish but big enough to pick by fall.

I have had some luck in past years with peas, it really is hit or miss, depending on the weather. Radishes are so quick that I can always sow some later and get a harvest, even if they are not really large. I plan to do some lettuce this fall and make a mini greenhouse out of the boxes and see what I can get.