I have read articles that indicate specific soil temperatures are required before planting certain plants in the spring. How do I determine what the soil temperature is? Are there actual soil thermometers to use?
The uptake of water and nutrients is greatly affected by soil temperature. Seed germination is also affected by temperature. Planting before the soil is sufficiently warm can delay or prevent the establishment of many plants.
As you might imagine, not all plants are the same. Cool season crops like peas, cabbage, lettuce and onions can be planted and will establish when soil temperatures are still quite cool (45 degrees Fahrenheit). Tomatoes and peppers, however, will not grow well until soil temperatures reach 59 degrees or more. Melons and cucumbers need temperatures in the middle 60’s to take off. Most flower and herb seeds require a minimum temperature of 62 degrees, but will germinate faster if warmer.
Soil thermometers are available at many garden centers. Expect to pay between $10 and $20 for a good thermometer or a good deal more if you want something fancy. Insert the thermometer 4 to 6 inches in the ground for your reading. Remember that not all areas of your yard will warm up at the same time. Soil type, sun exposure and adjacent structures all influence the rate of warming. Your soil thermometer can take the guesswork out of the equation and allow you to get the earliest possible start.