Question: How critical are soil temperatures in my gardening activities? Would it help if I had a soil thermometer? Where are they sold?Answer: Many things are impacted by the temperature of the soil. A couple of prominent examples are sowing bermuda seed and planting caladiums, both of which should wait until soil temperatures exceed 70 degrees on a regular basis; and planting tulips after the soil temperature drops to the low 50s for three consecutive days in early winter. Many other plants are also impacted through the course of the year.
You can buy soil thermometers in well-stocked hardware stores and garden centers, from mail order catalogs and online. Many people use a heating/air conditioning contractor’s pocket thermometer. They’re small, slender, and easily inserted into garden soil.