Even novice gardeners have a vague notion that rotating their vegetables in the garden is important to keeping disease and insect pests under control. However, all but the most experienced gardeners can occasionally make the error of rotating their crops incorrectly and defeating the purpose. This happens when gardeners move plants to a new location without paying attention to the plant family it belongs to.
Because plant families are typically susceptible to the same diseases and insect pests, and generally deplete the soil of the same nutrients, identifying the plant family for each vegetable you grow is important. Most vegetables fall within four plant families. The solanaceous plant family includes potatoes (Solanum tuberosum ), tomatoes (Solanum lycopersicum L.), eggplant (Solanum melongena) and peppers (Capsicum annuum); cucurbits include cucumbers (Cucumis sativus), melons (Cucumis melo), squash (Cucurbita maxima, Cucurbita pepo, Cucurbita moschata) and pumpkins (Cucurbita maxima, Cucurbita pepo, Cucurbita moschata, Cucurbita argyrosperma); cole crops include cauliflower (Brassica oleracea var. botrytis), broccoli (Brassica oleracea var. botrytis), cabbage (Brassica oleracea var. capitata), kale (Brassica oleracea var. acephala) and brussels sprouts (Brassica oleracea var. gemmifera); and legumes include beans (Phaseolus vulgaris) and peas (Pisum sativum).
Several common garden vegetables don't fit into those groups. Penn State University Extension recommends considering these plants to be members of families with similar cultural needs. For instance, corn (Zea mays) can be included with the cucurbits, and lettuce (Lactuca sativa) with cole crops. Other vegetables such as carrots (Daucus carota var. sativus) and onions (Allium cepa var. cepa) can be among other plant families.
Designing Your Garden
Dividing your garden into four sections allows you to devote one section to each plant family. Although you can create blocks of rows to devote to each section, formal dividers are not necessary. Sections do not need to be the same size, but rotating the plant families is easier if each section is approximately the same size. As an alternative, sections can be subdivided so that you plant two plant families within one section and plant another plant family in two sections, depending on the vegetables you grow and the amount of space they require. For example, you may wish to devote only one-half section to cole crops while planting two sections of cucurbits.
Sketching the Garden
Making a paper sketch of your garden that shows which vegetables you have planted in which section and dating the sketch allows you to review your planting design from the previous year. By saving the designs for several years, you can track how you rotated your crops. Some gardeners prefer to label the sections by number or letter to make rotating easier.
Moving your plant families to the right to the next adjoining section each year avoids confusion and makes planting easier. You may need to adjust your sections, particularly if you chose to subdivide your sections for smaller amounts or chose to use two sections for one plant family. The object is to move the entire plant family to a new location each year.
Sometimes, it is difficult to rotate crops such as corn or tall peas as they must grow where they don't shade other plants. One alternative is to grow them on the western border of your garden one year and the northern border the next. Permanent trellises or fences may also dictate where you plant specific plants. In this case, removing all garden debris from the garden, particularly when infested with insects or disease is vital. Testing the soil at least once every three years and following the instructions for amending the soil keeps nutrients in balance.