I’m not sure “crop rotation” applies to small garden beds, especially when they are tightly spaced as in OGCG, but the principle holds true: you can’t plant the same thing, year after year, without depleting key nutrients those plants need and increasing pests and diseases associated with those plants.
Anna provided the article at right to help explain. The article suggests a rotation of:
Year 1: tomatoes
Year 2: brassica (cabbage) family
Year 3: onion family
This article will be updated and expanded in the near future.
Also, an article on garlic pests will be developed (garlic needs rotation of at least three years).