What's Your Soil Temperature?

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Spring will be here in a few hours although it doesn't feel like spring out with snow flurries coming down as I type this.  I got curious today and took my meat thermometer, yes I said meat thermometer out to see how warm my garden soils were. Soil thermometers can also be purchased if you don't want to use your meat one. The first spot I checked was inside my cold frame where I plant early lettuce.  It was around 50 degrees.  My lettuce and spinach that I stared in plug trays will be ready to transplant in here this weekend.


Temperature in my cold frame.


I checked several other gardens and they were all consistently 45 degrees. 


Some cool season crops like broccoli, cabbage, beets and carrots can germinate at 40 degree soil temperatures, however many of our warmer season crops like the soil to be around 55 - 60 degrees or even warmer.  The same temperatures should also be used when planting transplants outside. Air temperature needs to be kept in mind as well. If there is a threat of heavy frost or freeze, cover them.  Also keep in mind if it's cold and damp, seeds that have not yet germinated might rot. Once they do germinate the small seedlings could rot from being to cold and wet.


Another garden task that many folks do to soon is applying mulch.  Mulch ideally should not be applied to garden beds until your perennial plants start to wake up and the soil temperatures are around 60 - 65 degrees, sometime in May.  Waiting until May allows the soils to warm up and dry out a bit before applying the mulch.


Consistent weather will be here before we know it but until then refrain from applying mulch to cold wet soils.


I challenge you to measure your soil temperature and let me know how warm it is at jagger.6@osu.edu.