By Judy Salveson, Extension Master Gardener
Crop rotation has long been known as an effective means for maintaining soil fertility and controlling pests and diseases. We know that planting the same crop in the same place every year can lead to problems, but what can you do if you have only one raised bed in your small garden?
The vegetable garden at Potomac Overlook Regional Park, with many beds and a wide variety of plants, has a plan for rotating different crop families into four different places over a four-year period so that the same crop family is not planted in the same place again for four years. In a garden with fewer beds and plant families, a three-year rotation is often recommended. Even a two-year rotation is better than planting the same crop in the same place every year.
If you have only one established bed at least 4 feet wide and 8 feet long, each half can be treated as a different place for plant rotation. Consider other sunny places in your yard for additional rotating locations. You do not need to add another raised bed. A 4×4 spot in a sunny location is sufficient to establish another bed for four tomato plants. You can tuck small irregularly shaped beds into suitably sunny spots and border them with stones or bricks. A sunny front yard may have room for an attractive border of flowers, herbs, and vegetables. Consider extending your rotating growing spaces with large pots. Strong, lightweight, and inexpensive cloth pots with handles are permeable for air and water, easy to move, and available online in a variety of sizes. Peppers need at least a 5-gallon pot to thrive. Most tomatoes do better in bigger ones. Consider a 15-gallon cloth pot for fingerling potatoes or cucumbers.
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Decide what vegetables you want to grow every year and identify the crop families to which they belong. Plants in the same botanical family share similar soil needs and suffer from similar pests and diseases, so they should not follow each other in rotation. These are some frequently planted vegetable families:
- Solanaceae: tomatoes, peppers, eggplant, and potatoes
- Cucurbit: cucumbers, squash, pumpkins, and melons
- Legume: bush beans, pole beans, and peas
- Brassica: kale, radish, broccoli, turnips, and mustard greens
- Allium: onion, scallion, and garlic
- Goosefoot: beet, Swiss chard, spinach
- Composite: lettuce, endive, and escarole
- Umbel: carrot, dill, parsnip, lovage, and parsley
Photo © Judy Salveson
For a three-bed rotation, identify the major crop families you want to grow. Greens and roots come from a variety of different families and either can be rotated as a group. Designate a different planting area for each family or group each year.
If the only suitable place for your tomatoes is in your one raised bed, alternate their position in the bed from one side to the other each year and plant crops from another family on the other side. If one half of your one raised bed is not big enough for both tomatoes and peppers, plant peppers in 5-gallon pots or in a sunny border.
Never follow a crop from the same family with another crop from the same family into the same place as the season before.
Legumes add nitrogen to the soil with the nitrogen fixing nodules on their roots. Nitrogen hungry Solanaceae or Cucurbits are happy to follow legumes in a rotated bed.
Brassicas have a unique ability to suppress the growth of some disease-causing bacteria, fungi, and nematodes. Disease prone crops might be happy to be planted in the soil where brassicas were grown the season before.
Remove dead and diseased plant material from your beds promptly to limit the spread of disease and enrich your beds seasonally with a layer of good organic matter, such as well composted leaf mulch or home-grown compost. Keep good records of where you plant each crop each season so that you can avoid planting the same crop family in the same place next year.
For more information on rotating crops in a small garden, refer to MiniFarming: Self Sufficiency on 1/4 Acre by Brett L. Markham (2010).