How to Measure Soil Temperature Before Planting

Knowing when to plant can be tricky, but timing is critical, especially if you have short growing seasons. Checking the soil temperature is one way to help you decide when to plant. Many gardeners focus on air temperature when deciding when to plant, but soil temperature is often a more reliable indicator of when seeds will germinate and thrive. Learn how to measure the soil temperature correctly and use the “Soil Temperature Guidelines for Seed Germination Chart” in this article to learn the best times to plant. 

Article Outline:

• Why should you check your soil temperature before you plant?
• How to Check Your Soil Temperature Before Planting
• Soil Temperature Guidelines for Seed Germination Chart

Why should you check your soil temperature before you plant?

Soil temperature affects biological and chemical processes. Seeds require a specific range of temperatures to trigger the enzymatic activities necessary for germination.

Simply put, if the soil is too cold, seeds stay dormant or rot instead of sprouting. On the other hand, if the soil is too warm, seeds might not germinate or dry out too quickly. Additionally, when soil temperatures are too high, plants can have difficulty taking up water and nutrients.

A soil temperature reading helps increase the chances of successful germination and healthy plant growth. 

How to Check Your Soil Temperature

To measure soil temperature:

1. Use a reliable soil thermometer. This is the one I use.
2. Take readings first thing in the morning. It’s essential to check the soil temperature when it’s most stable, typically in the early morning. This timing avoids the peak heat of the day, providing a more accurate measure of the soil temperatures your plants will face most consistently.
3. Insert a soil thermometer into the soil at the depth where the seeds will be planted.
4. Wait for the gauge to settle on a number.
5. Note the temperature while the probe is still in the soil.
6. Measure over several days to get an average temperature if possible.

Once you have your soil temperature, compare it to the guidelines below to determine the best planting time.

Soil Temperature Guidelines for Seed Germination Chart

For the best results, invest in a reliable soil thermometer, monitor soil temperatures regularly, and refer to your local planting guide and this soil temperature guide as you plan your planting season.

References:

California Master Gardener Handbook, 2nd edition, Regents of the University of California, Division of Agriculture and Natural Resources, Publication 3382 (Table 5.2, page 114).

Colorado State University Extension. “Plant Growth Factors: Temperature“.

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