All About Soil Thermometers

They help you tell time

A quality soil thermometer is going to be useful during those hesitant spring months when you just don't know if it's time to plant the tomatoes.  There are a surprising amount of options out there, all claiming to be the one you need.  Just in case you are easily duped by verbose marketing, "good for use with soil, compost, mushrooms, heated seed beds, and plant rearing," means that this item may be used to measure the temperature of dirt. 

What to look for

The first thing you want is the proper length.  Six inches is all you need for gardening, any more and you are conducting expensive geology experiments for your rose garden.  You shouldn't pay more than eight dollars for a basic soil thermometer.  They look like meat thermometers but are a bit longer and may have bigger dials. 

Other features depend on personal preference.  Are you going to want one that can be read while in the ground?  Many display the temperature on the side and must be removed from the ground to be read.  If you want to leave it in the ground for long periods of time, you probably want a thermometer with a brightly colored head so you 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. 

Consider digital

Overall, the digital soil thermometers are the best deal.  At about $17, they are a bit more expensive than the basic models, but some websites offer free shipping.  Some are shaped like pens to fit in your pocket and others are T-shaped, allowing a reading while the thermometer is planted.  Both styles are waterproof, store readings, measure in Celsius and Fahrenheit, and come with a warranty.  And, if you don't mind multi-purposing your thermometer, they are also appropriate for use in the kitchen and lab.

More information on soil thermometers