Should I mulch tomatoes and peppers at this time of the year? I know that they both love warm soil and am worried that mulching them might cause the soil to be colder even though I like to preserve the moisture in my raised beds with mulch.
Lake Toxaway, N.C.
Dear Lee –
The conventional wisdom is to wait until the soil warms to apply organic mulch. You can monitor that temperature with a soil thermometer. Sixty degrees is good for peppers. Synthetic mulch is widely used in commercial vegetable production. A thin single-use plastic is available at most feed and seed stores. We use a version of this material in our greenhouses under tomatoes and cucumbers which has a white and a black side. The white side up reflects light up under tomato leaves and increases yield. It does slow the heating of the soil but that’s usually not a problem in a heated greenhouse.
Outside we use a different type of synthetic mulch under tomatoes, a woven landscape fabric (see Ask Tom April 2010). Its black color seems to help warm the soil as well as helping keep the soil evenly moist as organic mulch does. It provides little insulation so it can be installed before the crop is transplanted. My theory is that its main mechanism for soil warming is to block radiant heat loss at night. It also probably provides some protection from low temperature winds. Here is a photo of landscape fabric under a crop of lettuce.
Thanks for your question.
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Tom Elmore is co-owner and operator of Thatchmore Farm in Leicester NC. He has grown certified organic fruits and vegetables for 25 years and serves on the Boards of the NC Greenhouse Vegetable Growers Association and the Organic Growers School.