How to Use a Soil Thermometer

A little effort goes a long way

Many sources contend that the correct soil temperature is equally as important to a flourishing crop as the right time of year.  Planting in soil a bit too cold could result in seed rot, slow germination, growth problems and disease.

Just 10 degrees F in soil temperature will delay cucumber germination an entire week, and peppers plants can be stunted all season if planted under 70 degrees F.  Indeed, properly using your soil thermometer could save you from a season scarce of your favorite vegetables. 

The calendar says 'plant'

Old farming wisdom about planting when the ground is workable is rather obsolete now.  Instead, shoot for consistent ground temperatures over three mornings.  For planting seeds, get a measurement at about two inches of depth.  If you are transplanting, measure four to six inches deep.  Of course, it is best to wait a few minutes before taking a reading.  The following information will get you on the right track.

60 F - tomatoes, cucumbers, snap beans

65 F - sweet corn, lima beans, mustard greens

70 F - peppers, watermelons, squash, southern peas

75 F - okra, cantaloupe, sweet potatoes

Finally, remember to make it easy on yourself when using the soil thermometer. Many display the temperature on the side which means you must take it out of the ground to read it.  If you want to leave it in the ground for long periods of time, consider purchasing a thermometer with a brightly colored head so you can locate it quickly.  If you are going to be measuring the temperature of a compost pile, you'll want a soil thermometer with a range past 160 degrees F.  Some thermometers don't read past 140 degrees F and would be useless in killing off resilient pathogens and weed seeds. 

Using a soil thermometer is not quite as easy as it sounds, but almost.

More information on soil thermometers