Rotating backyard crops: Get to know the family

Rotating your garden crops can help prevent the buildup of soil-borne pests. But this is not always easy in the backyard garden because so many of the vegetables we grow are in the same family, and therefore are susceptible to the same diseases.

Tomatoes, for example, are related to potatoes, peppers and eggplant. Cucumber, squash, pumpkins, cantaloupe and watermelon all are Cucurbitaceae, while broccoli, Brussels sprouts, kale, radishes, cabbage and kohlrabi are in the Brassicaceae family. Every plant belongs to some family, and these are just a few examples.

It is important to know a little about plant families, especially if you have any problems with diseases in your garden. Last year, for example, one of my tomatoes died of bacterial canker, a soil-borne disease. It undoubtedly was infected when I bought it as a seedling, and for me, that diagnosis has at least two results in addition to losing the plant.

One, the area where that plant grew in my garden is now infected, and I cannot plant anything related to tomatoes there for three years, because other tomatoes, or any vegetable in the same family, could become infected. And two, I will be very cautious about buying plants from that grower in the future.

So what can I do? I could plant corn, cabbage, carrots or leafy greens in that section, as they are not in the same plant family as tomatoes, and for the most part soil-borne diseases do not readily move from one plant family to another.

Other options include solarization, which means putting heavy, clear plastic over the area for the hottest part of the summer. This will pasteurize the soil and help rid it of weed seeds in the bargain. Or, I could plant a cover crop and not use that area for a while.

Sanitation is especially important when a disease occurs. I removed every bit of the infected plant, including the root and dropped fruit, and put it in the garbage. This is one of the reasons, by the way, that gardeners need to do a good fall cleanup. Don't provide a winter resort hotel for pests of any kind!

If you grow plants in containers, it is relatively easy to prevent soil-borne problems. Simply add the soil you used this year to the compost pile, clean the container well, rinse it with a 10-percent bleach solution, and use fresh soil next year.

Keep in mind that many heirloom vegetables are not very resistant to plant diseases. What this means is that you should keep an especially watchful eye out for problems you see developing in heirloom vegetables, and take necessary steps right away so the problem does not spread.

If you are uncertain about what is causing a plant problem, take a portion of the plant (and a picture, if you can) to the free Master Gardener plant clinic at the Southern Oregon Research and Extension Center, 569 Hanley Road, in Central Point. Call 541-776-7371 for hours they are open. The plant clinic operates at the Growers Markets in Medford and Ashland, too, when they are open.

Coming up: Three hands-on pruning workshops are scheduled for upcoming Saturdays. Grape pruning is scheduled for Feb. 9; backyard fruit-tree pruning is Feb. 16, and rose pruning is March 2.

All of the workshops will be held at the Southern Oregon Research and Extension Center and will cost $10 each. Call 541-776-7371 to register.

Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at

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