Carrots take a long time to be fully done; 100 days or so. Would not recommend putting those in an area where you want to grow warm-weather crops. Peas most likely would work. What I've typically done is make a row of peas on a fence and after it begins to get warmer, I'll start cucumbers on it. So the peas will produce and grow as the cucumbers are beginning to sprout. Works quite well. Spinach is a cool-weather crop and should do just perfect for your rotation plan. Onions will not; they also need full sunlight; the larger the onions, the larger the bulbs. They also take 100 or more days for northern varieties. I cannot comment on kale, beets, chard, or parsnips since I don't grow those. Here is a link that might be useful: My Garden Blog

I don't have Caroline or Anne. I see they are also 'everbearers'. Basically we dug up 200+ starters at my mom's and did the mass planting. Within the plot I have no weed issues as they get totally choked out. However is encroachment on the edges, but nothing a weed whacker and heat wont take care of. By eliminating all of the plant material in the fall I also take care of rabbit hide-outs and keep disease in check. I burn any prunings. In my current situatoin it would have been great to have berries in July too, though. As H-man wrote, and I concur, it's nice to have a summer crop for browsing. We'll see what the 30 degrees did later on, but that's half our crop! Noogy Noogy

Rotating plants between beds comes to us from large scale farms where the need to rotate for soil nutrient replensihment also gave some indication that if you planted crop A a good distance from the field it was in the previous year problems with insects and diseases was less. Unless you can move your plants a least 300 feet from where they were last planted every year crop rotation is an unnecessary exercise, especially if you get your soil into that good, healthy condition that will grow storn and healthy plants less desirable to insect pests and plant diseases. If you have trees, shrubs, and perennials growing in the same place every year why would you not move them also, if crop rotation is that important? I have had people tell me that perennials are different from annuals, but they cannot tell how they are different. If you are a "conventional" gardener rotating your plants around might make sense so you don't pollute on bed with all the poisons needed to control the problems that "conventional" gardening brings, but a good organic gardener with a good, healthy soil will not have that much of a problem. If an organic gardener does have problems with insect pests and plant disease they need to look at their soil to see what they problem is because they apparently have not gotten to that good, healthy soil stage, yet.

buckwheat is a summertime cover crop that I use for weed suppression for 4 week period. it doesn't like cold weather. I am in zone 5 and my winter cover crop is annual rye or cereal rye with tillage radishes or turnips mixed in. you are in zone 7 but I bet it is still to cold for buckwheat