Do you always plant your garden the same way? Maybe there’s a permanent tomato trellis, and your corn patch is usually on the north side? If so, consider changing things up this year: your garden will thank you.
For thousands of years, ‘crop rotation’ has increased vegetable and grain yields. In ancient China (around A.D. 1,000), summer rice and soybeans were alternated with grains, vegetables, or legumes in the winter. Texts from ancient Rome describe which crops should be grown before or after others on successive years. Crop rotation is still practiced on conventional and organic farms throughout the world. While most vegetable gardens operate on a smaller scale, the same concept can improve your soil and control certain pests.
Soil quality can make or break a garden, and how you rotate plants either adds nutrients or strips them away. If you always plant the same thing, let’s say pumpkins, in the same corner of your garden, the soil will eventually be depleted of the exact nutrients that are most needed by pumpkins, resulting in fewer and smaller pumpkins. But if you plant pumpkins somewhere different every year, they will have a better shot at getting the nutrients they need.
Some plants, like corn and tomatoes, are ‘heavy feeders’ that take more nutrients from the soil. Alternating their location with lighter feeders, like carrots or beets, is a good idea.
Legumes, including peas, beans, and clover, actually improve the soil. Legumes make nodules on their roots where bacteria cluster and convert nitrogen from the atmosphere into nitrogen that plants can use. Pull up a legume from your garden this summer: if you see these nodules, this plant-bacteria partnership is fertilizing your soil. (For more information, see my post here.)
In addition to conserving soil nutrients, crop rotation can protect against garden pests and pathogens. According to this 2009 planning manual for organic farmers, pests that have specific plant hosts (including corn root-worm and potato beetles) die when their plant hosts are moved away. Likewise, bacterial infections of tomatoes and peppers usually can’t keep up when the plants are moved to a new location.
Convinced? Here are some ideas and examples of how to do this in your garden.
Plant species are grouped into ‘families’, or groups of species that share certain traits because they are closely related. This year, try grouping all the members of each family together in the same area, or plot. Next year, switch your families around so that each family is growing somewhere new.
Mentally divide your garden into 3 or 4 equal parts and rotate in an orderly progression. This way each plot grows the plant families in the same order over 3 or 4 years. Your garden plots do not need to be rectangular (once I had a semicircular garden), although ideally they will be approximately the same size.
The following is a simple example of a 4-year rotation plan:
Keep in mind that you can add multiple species from the same family to each plot. For example, grow parsnips, parsley, and dill with your carrots (because they are in the same family) in plot 1. Peas and beans share a family, as do tomatoes, peppers, potatoes, and eggplant. Squash (including summer and winter squash) are grouped with pumpkins, melons, and cucumbers. Radishes, kale, broccoli, cauliflower, turnips, and arugula are all in the same family. You can combine multiple families in the same plot (such as radishes and kale with carrots in plot 1), but make sure you’re not growing members of this family anywhere else at the same time.
There are endless variations on this theme. Experiment and individualize your rotation plan based on how much space you have, what grows well in your garden, and what you like to eat. Draw a map of your garden each year so you remember where everything was grown.
Here in garden zone 5, I can fit two quick-growing vegetable crops into the same year in many of my plots. For example, I usually grow spring dwarf peas before winter squash in the same space, a practice also suggested in this planning guide. Make sure you add a thick layer of compost prior to each planting of every non-legume family (see my post on compost here).
Here is an example of a more complicated rotation:
If your garden is located in a mild climate or covered with a hoop house during the winter (for how-to advice, click here), you can get even more creative:
The authors of Crop Rotation on Organic Farms: a Planning Manual interviewed twelve expert organic farmers about crop rotation. The following points are paraphrased from their “examples of conventional rotation wisdom”, which are relevant to the vegetable gardener as well as the farmer.
- Don’t plant the same family in the same place ‘too often’.
- Consider growing cover crops during the winter or at other times between your vegetables. [Cover crops are grown to enhance or protect the soil, not to be harvested, and include legumes like ‘hairy vetch’.]
- Think about your plants’ roots: ideally, deep- and shallow-rooted plants follow each other.
- Grow legumes that fix nitrogen before plants that need lots of nitrogen.
- Don’t grow two seasons of root crops right after each other.
Planning your garden with these principles in mind will enhance your soil and reduce pests and diseases in your garden.