Rotating crops is very important even in a small vegetable garden. The point is to avoid planting the same plants or plants in the same family in the same spot year after year. This is beneficial to the garden in several ways. Crop rotation is used to maintain soil nutrient levels, discourage disease caused by nematodes, and to avoid providing the same plant over and over to insects that feed on a certain type of vegetable.
The best way to keep track of your crop rotation plan is to make a map of your garden each year and each season. This can easily be kept for many years in a small notebook. Nothing fancy is needed, just a simple map to keep track of what has planted in each row season after season. Keeping a notebook will also help you to remember the varieties of vegetables you've planted each season. It also gives you a place to jot down notes in the margin about what worked best and worst in the last season.
A good garden map will also give you an opportunity to try different planting methods, such as companion planting or the scatter technique that some organic gardeners use. Many organic gardners scatter a type of vegetable all over the garden instead of planting in a row. In a larger garden this may make the insects work harder to find a particular type of vegetable thus ensuring that some plants are not damaged as much as others.
Depending on the size of your garden a crop in a particular family should never be planted in the same area within 3-6 years. So if you have a small garden, plants in the cucumber/gourd family should not be replanted in the same row until the 4th year. If your garden is larger and you have more space then it can be even more beneficial to extend the rotation to the 6th year. Experienced gardeners not only rotate crops in their garden but most include cover crops to provide soil with organic matter, nitrogen and to keep erosion to a minimum. These crops are usually clovers, alfalfa, ryegrass, oats or other legumes that can be turned under after growing for a few months.
Following is a short plant list, although not comprehensive, it should give any gardener an example of common plants in the same family and give you a good start in beginning a crop rotation plan.:
Apiaceae- The parsley and carrot family. Includes carrots, celery, dill, parsley and parsnips.
Asteraceae- The sunflower and daisy family. Includes artichokes, dandelions, lettuces and endives.
Brassicaceae- The mustard and cabbage family. Includes arugula, broccoli, cabbage, cauliflower, collards, kohlrabi, mustards and radishes.
Cucurbitaceae- The cucumber and gourd family. Includes squash, cucumbers, gourds, melons, and pumpkins.
Fabaceae- The legume family. Includes beans, peas, peanuts, soybeans, lima beans, and sugar peas.
Liliaceae- The lily family. Includes asparagus, garlic, onions, shallots and leeks.
Solanaceae- The nightshade family. Includes eggplants, tomatoes, peppers, potatoes and tomatillos.