Crop rotation will benefit vegetable crops in two ways: first, it will prevent the build-up of soil-borne pests and diseases; second, it will allow for the replenishment and efficient use of soil nutrients.
Crop rotation is the practice of growing different crops, rather than the same vegetable or members of the same family of vegetables, in the same place each year.
To minimize pest and disease problems and to help renew soil nutrients, members of the same plant family should not be planted in the same part of the garden more than once every three or four years.
Vegetable insect pests tend to feed on similar plants and members of the same plant family. For example, an insect pest that attacks and eats cabbage will lay its eggs before it dies. If cabbage or a member of the cabbage family is planted in the same spot the next year, the eggs of the insect will hatch and the pests will find exactly the food they need to continue the pest life cycle. Soilborne diseases–fungi, bacteria, and viruses–also can be hosted by specific plants as well. Removing host plants or alternating unrelated plants into the garden can break the cycle of pests and disease.
Crop rotation also helps prevent soil nutrients from being depleted. Vegetables draw upon a wide range of soil nutrients for growth: nitrogen, phosphorus, and potassium are the key or major soil nutrients. Members of the same vegetable family usually draw the same nutrients from the soil.
Crop rotation will prevent the soil from wearing out: heavy nitrogen, phosphorus, and potassium feeding crops such as tomatoes are rotated with soil-building crops such as beans which add nitrogen to the soil and then with light-feeding crops such as onions.
Major plant families and some notes on crop rotation:
• Onion Family (Amaryllis Family, Amaryllidaceae): Garlic, onions, leeks, shallots. These are light feeders. Plant these after heavy feeders or after soil enrichers such as beans.
• Cabbage Family (Brassica, Cruciferae): Broccoli, Brussels sprouts, cabbage, cauliflower, Chinese cabbage, collards, cress, kale, kohlrabi, radishes, turnips. These are heavy feeders. These crops should follow legumes. After these crops allow the garden to go fallow for a season or plant a cover crop or add plenty of compost and organic matter to the garden.
• Lettuce Family (Composite, Daisy Family, Asteraceae): Artichokes, chicory, endive, lettuce. These are heavy feeders. Follow these crops with legumes.
• Beet Family (Goosefoot Family, Chenopodiaceae): Beets, spinach, Swiss chard. These are heavy feeders. Follow these crops with legumes.
• Grass Family (Graminae): Grains–corn, oats, rye, wheat. Follow these crops with members of the tomato or Solanaceae family.
• Bean Family (Legume, Leguminosae): Beans and peas, clover, vetch. These crops enrich the soil, soil builders. Plant these crops before or after any other crop family with one exception–do not plant beans after onions.
• Tomato Family (Nightshade Family, Solanaceae): Eggplant, peppers, tomatoes, potatoes. These crops are heavy feeders. Plant these crops after members of the grass family. Follow these crops with legumes.
• Squash Family (Cucurbitaceae): Cucumbers, melons, summer and winter squash, pumpkins, watermelon. These crops are heavy feeders. Plant these crops after members of the grass family. Follow these crops with legumes.
• Carrot Family (Umbellifer Family, Umbelliferae): Carrots, celery, anise, coriander, dill, fennel, parsley. These are light to medium feeders. These crops can follow any other group. Follow these crops with legumes, onions, or let the garden sit fallow for a season.
You can use the notes above to accomplish crop rotation or you can simplify the rotation as follows:
Simple Four-Year Crop Rotation Plan:
To follow a simple four-year crop rotation, divide your garden into four areas or plots: Plot One, Plot Two, Plot Three, and Plot Four. In each of the next four years, grow a different crop or different members of the four crop families in a different plot following this rotation:
• Plot One: Tomato family (year 1); Others–see list below (year 2); Bean family (year 3–but avoid planting beans where onion family crops have just grown); Cabbage family (year 4).
• Plot Two: Cabbage family (year 1); Tomato family (year 2); Others–see list below (year 3); Bean family (year 4–but avoid planting beans where onion family crops have just grown).
• Plot Three: Bean family (year 1–but avoid planting beans where onion family crops have just grown); Cabbage family (year 2); Tomato family (year 3); Others–see list below (year 4).
• Plot Four: Others–see list below (year 1); Bean family (year 2–but avoid planting beans where onion family crops have just grown); Cabbage family (year 3); Tomato family (year 4).
This four-year crop rotation intersperses members of the other vegetable families among members of the Tomato, Bean, and Cabbage families, and Others. Here is how they are grouped:
1. Tomato Family and others (Solanaceae family)
Celeriac and celery
2. Bean Family (Leguminosae family)
Broad (fava) beans
French (green) beans
3. Cabbage Family and others (Brassica family)
Calabrese (Italian sprouting broccoli)
Squashes, zucchini, and pumpkins (marrow and courgettes)
Garlic–avoid planting beans in the same location after garlic
Leeks–avoid planting beans in the same location after leeks
Onions–avoid planting beans in the same location after onions
Shallots–avoid planting beans in the same location after shallots
Not included in crop rotation are perennial vegetable crops that grow in the same spot for several years in a row. Perennial crops include:
Small garden crop rotation:
No garden is too small for crop rotation. A simple garden map showing where each crop is planted will help you plan and plant a different crop in that spot next year. To plan crop rotation in a small garden, map out strips or blocks–rows or square feet–and avoid planting vegetables from the same crop family in that spot more than once every three years.