Solarization

September 2010

We have a raised garden which we have planted for ten years. My question is that every year my tomatoes look beautiful until they begin to put on tomatoes. Then the vines begin to turn yellow and no amount of spraying or watering seems to help. Is the soil just needing something or should we just not use this garden for a year and cover it with plastic to maybe rid it of the bacteria or whatever causes this blight. Is there anything I can put into the soil to help it?

We strongly encourage crop rotation--not planting in the same spot for three years. When you plant over and over again in the same spot, diseases build up and hit you earlier and earlier each season. While there are some pesticides for certain diseases, many of the soil borne problems are not covered. Solarize your soil now. You are getting a little late for 100% effectiveness, but try. Till the soil, thoroughly wet it and cover with clear plastic for at least 6-8 weeks. Test the soil this fall and see what the pH is and what your nutritional levels are. When you choose new plants next spring, look for disease resistance--VFN following the name. Try to divide the bed into thirds and plant one third with tomatoes next year, the next year in a different third and then the latter third in the third year. This can help.

June 2010

Is there any way to treat soil that would help fight tomato wilt? The only information I can find in garden books is to "buy disease resistant plants" and throw away the ones affected. I bought disease resistant plants and for the second year in a row, my tomato plants are healthy and have tomatoes on them one day and are wilted and dead the next. It is very discouraging. Can I plant anything in the fall (like clover) that might aid in cleansing the soil?

Many tomato diseases are soil-borne. That means they persist in the soil for years and can attack your tomatoes quicker each season. Planting disease resistant varieties helps, but only to a point. For one thing, disease resistance doesn’t cover every disease out there. Secondly, a new strain of the disease can build up especially if you plant over and over again in the same area. Rotating tomatoes in the garden is ideal, but again, that alone may not do the trick. The best idea is to sterilize your soil using soil solarization. Till the soil as deep as you can, then saturate the soil, getting it really wet. Once you have wet the soil, cover it with clear plastic, making firm contact between soil and plastic. Leave it covered for six to eight weeks between July and September and you should start off with clean soil next year. Cover crops such as clover and vetch can help to build up your soil, but do little to control diseases. You can also take a plant sample in to your local extension agent when you have the disease, they can pinpoint exactly which disease issue you have.

June 2008

Our daughter has moved in to her great grandmother's house and would like to reclaim the garden from the weeds and Bermuda grass so we can plant it next year. How do we do that and can we keep the Bermuda grass in the yard and not in the garden?

If you aren’t planning to use it until later—even this fall, you can solarize the site now and kill out most of the grass and weeds. I would scrape the surface free of as many of the weeds and grass as possible, then till the soil and wet it thoroughly. Once wet, cover the site with clear plastic, getting firm contact between the soil and the plastic. Weigh down the sides with soil, rocks or bricks to exclude air. Leave it covered for two to three months this summer and you can generate enough heat under there to kill out the weeds. You could then plant a fall garden, or if you want to wait until next spring, leave it covered until you plan to plant. Bare, exposed soil tends to invite weeds and grass.

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