Vegetable garden rotations

A brief mention of rotating vegetables in a talk yesterday morning encouraged a question about how to rotate garden crops -- important for a sustainable (organic) kitchen garden, simple in concept, but sometimes challenging in practice.

The principle is simple: rotate crops that are grown in a single area by plant family. There are a number of plant families represented in common vegetables, but not so many that it's easy to avoid repeat plantings.

Ground rules:

Don't plant tomatoes, peppers, eggplants, or potatoes (tomato family: Solanaceae) in the same area for 3 (preferably four) years, ditto with kale, broccoli, cabbage (mustard family: Brassicaceae). Alternate plantings with lettuce, chicory, marigolds (in the Asteraceae, or daisy family), carrots, parsley, fennel, or dill (in the parsley family: Apiaceae), onions, garlic, and shallots (in the onion family: Alliaceae), beans and peas (in the pea family: Fabaceae), squash and gourds (in the squash family: Cucurbitaceae), or beets, turnip, or chard (in the beet family: Chenopodiaceae). Wheat, rye, barley, and oats aren't commonly grown in home gardens, but make a great cover crop rotation, being in the grass family: Poaceae.

Some plant families are more disease-prone (because we grow them all the time) than others. Tomatoes, peppers, squash, and green beans fall in that category.

It's important not to plant vegetables in the same family year after year because of pest buildup-- soil critters like root-knot nematodes, fungal problems such as fusarium wilt, and presence of larval pests like squash-vine borers LOVE having their hosts there year after year.

I'm learning that lesson first hand.

My main vegetable garden isn't that big. It's basically a long row of five blocks (roughly 5 X 5 ft) loosely adhering to the Square-Foot Gardening principles described by Mel Bartholomew. They're a little bit too big to reach in easily, but simple to dig by hand. Each block is separated by stepping stones and a mulched path, and edged by gray fieldstone.

I like to play around with my beds and mix up different vegetables, herbs, and flowers, and do NOT have a great record-keeping orientation, so after growing tomatoes, peppers, and 'cole' crops in various places in the blocks, I'm starting to see a build-up of soil-based problems for these common species in the main vegetable garden after the 10 or so years I've been gardening there, root-knot nematodes and fusarium wilt (I think) in particular.

The satellite garden, started 3 years ago, provides a more expansive opportunity for rotations and cover crops (very helpful for soil replenishment and dealing with soil difficulties).

So, I'm planning on being much more scrupulous about rotations (I WILL keep a plan of what I planted, I hope), using cover (and trap) crops, and introducing predatory (supposedly) beneficial nematodes, in the coming months.

There are lots of sites that provide useful information about rotations. A quick Google search finds Yankee Gardener, an Iowa State University site, and a Texas A&M site at the top of the heap.