I gave an organic vegetable gardening class at the Community Garden at Holy Nativity on “Vegetable Rotations.” The eventual goal of the class was to explain how, when I did the initial design for the Community Garden, I’d integrated vegetable rotations into the design. The garden team is getting ready to plan their cool season plantings.

There are several reasons we rotate crops: plant diseases, pests, and soil nutrition (mostly nitrogen).

Methods devised for coping with these issues include rotation “over time” (rotation), or rotation “in space” (companion planting).

Different systems include:

• Polyculture, which is growing many different plant species in the same area of the garden. This is well described in Toby Hemenway’s Gaia’s Garden.
• Guilds, which is growing plants that have known compatibility in the same space in the garden. These compatibilities might mean nutrient compatibility, pest deterrence, etc. A well-known example of a guild is the Native American “3 sisters” of corn, beans, and squash. Linda Woodrow describes guilds very well in A Permaculture Home Garden.
• Conventional rotation, the block method of moving crops over one block each consecutive season. This is described in Rodale’s Vegetables. Sally Jean Cunningham (Great Garden Companions) has a simple system of “neighborhoods” which move over, block by block. Cunningham’s is a relatively easy place to start.
• A combination of methods, such as Emilia Hazelip’s “Synergistic Gardening.” Hazelip used rotations in time as well as her own form of guild-type groupings.

John Jeavons, in How To Grow More Vegetables, describes a very simple rotation where Heavy Feeders (corn, tomatoes, squash, lettuce, cabbage) in one season are followed by Heavy Givers (legumes, which means peas and beans), followed by Light Feeders (all root crops) “to give the soil a rest.” Jeavons throws in a few out of sequence vegetables, the Low Nitrogen Lovers (turnips, sweet potatoes, and green peppers), which he often plants following the Heavy Givers. In Jeavons’ book (available in many public libraries), he offers extensive charts which document which vegetables (even exotic ones) fall into which category.

Sally Jean Cunningham’s rotations are a step up in complexity. She groups plant “friends” and “family” by “neighborhoods,” and moves the neighborhoods in rotation. The Tomato neighborhood (tomatoes, peppers, eggplant, greens) is followed the next season by the Squash neighborhood (the “3 sisters” of squash, beans, and corn), followed by the Roots & Greens neighborhood (carrots, greens, onions), followed by the Potato neighborhood (potatoes, beans, peas). In Cunningham’s materials, she explains that plants in the tomato family need a 4 year rotation to avoid spreading fungal disease. Thus four seems to be the lowest number of plots one can have in a functional rotation.

In order to plan rotations, you probably need to know a little bit about plant families, because when Cunningham or Jeavons say “cabbages” it’s helpful to know that category includes collards, broccoli, cauliflower, and more! Suzanne Ashworth’s Seed to Seed is great for learning about plant families, as is “Plant Families for Planning Rotations,” a publication of Jeavons’ Bountiful Gardens.

In Southern California we are privileged to have a year-round growing season. This “blessing” can turn crazy-making if you don’t understand what to plant when. For planting guidelines for our unique climate, see DigitalSeed’s “Southern California Vegetable Planting Schedule,” or “Cool Season Vegetables” from the Master Gardeners of Santa Clara County.

In planning the Community Garden at Holy Nativity I merged many of these ideas. I divided the garden into 4 main patterns, each pattern becoming one of Cunningham’s “neighborhoods.” For our debut season, summer 2008, the Tomato pattern included basil, tomatoes, peppers (hot & mild), and eggplant. The Squash pattern included beans. Although we didn’t plant corn, I added sunflowers for fun. The raised beds which lined up along a wall, giving it afternoon shade, were designated the Roots & Greens pattern. Thus the leafy greens would be less likely to wilt in the summer sun. Cunningham’s Cabbage neighborhood was a bit of a problem. Since we were planting at the tail end of the spring season (June 14), I didn’t feel it was likely we would be successful with many cabbages, as these like the cool moist So. Calif. winters. I knew collards might make it, but we had some glitches in getting seedlings sprouted by our volunteers. Thus our erstwhile “cabbage neighborhood” became a catch-all with quinoa, chard, and some excess pumpkin plants.

The Southern California year round growing season adds complexity here. In a location with a frost, you have a fixed END to your season. The next season, it’s obvious, you start with the next “neighborhood” on your rotation palette. But here, where one vegetable finishes the season and the next one over is still growing, when does the season end? When do you shift to the next type of plant? It is clear that the gardener must decide upon a date, rather than the frost’s natural clearing doing it for you.

If we decided to switch neighborhoods as soon as each crop was finished, the bed that in summer 2008 held the squash neighborhood would receive the tomato neighborhood now, with the fall 2008 planting. Seems okay? Not really. If you chart such a rotation several years into the future, you soon discover that you are moving your neighborhoods across your beds in double time–twice as fast as our East Coast gardening friends. Recall the reasons for rotating crops. This rapid rotation works fine with the soil nutrition reason (if you’re using legumes and added compost) but it fails the test when you consider reasons such as plant pests and diseases. For these, researchers tell us we must have a period of years between plantings of the same plant family.

Thus at the Community Garden at Holy Nativity I decided to set an arbitrary calendar date. Anything planted in the C beds during 2008 will be from the squash neighborhood. After January 1, all plantings will be from the next neighborhood, the tomato neighborhood. In this fashion, we will have a full 3 years rest for the C beds before they receive squashes again. In other words, squashes will be grown in the C beds in 2008, in the D beds in 2009, in the E beds in 2010, and in the B beds in 2011. The squashes won’t return to the C beds until 2012.

This does mean that we’ll have two seasons (warm season 2008 and cool season 2008-2009) of squash neighborhood in the C beds. However if you look at the list of squash neighborhood, you’ll soon discover that most squashes are warm season plants, thus the cool season selections from the squash neighborhood list are less likely to cause disruption in the spacing of the rotation. We’ll let you know how it works!

Coming soon: I hope to post a pdf file of some of our worksheets, including the list of plants we put in each neighborhood.

For more information on Edible Landscaping and Vegetable Gardening in Southern California / Los Angeles, please see my list of resources at www.LegacyLA.net/EdibleLandscape.htm