Temperature for vegetable seed germination

Updated July 19, 2017

Temperature is an important factor of soil conditions to consider when planting vegetable seeds. Without proper temperatures, seeds will fail to germinate or will germinate poorly. Soil temperature should be taken by inserting a soil thermometer 3 to 4 inches into the ground.

Optimal Range

The optimal germination temperature range for most vegetable seeds falls between 23.9 to 35 degrees Celsius. Some vegetables' optimal temperatures are on the lower side, such as onions, lettuce, and parsley, while other vegetables are on the higher end, such as corn, cucumbers and summer squash.

Minimum Temperature

The minimum germination temperature for most vegetable seeds is between 4.44 to 15.6 degrees Celsius. Some vegetables, such as peppers and beans, require at least 15.6 degrees Celsius. A few vegetables, such as onion and lettuce, can tolerate minimum temperatures as low as 1.67 degrees Celsius.

Maximum Temperature

The maximum germination temperature for most vegetable seeds is from 29.4 to 37.8 degrees Celsius. Some vegetable seeds, such as corn and cucumber, can tolerate temperatures above 37.8 degrees Celsius. Generally, the optimal temperature is about -9.44 degrees C less than the maximum temperature.

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About the Author

David Orr has written professionally since 2009. He has written about issues relating to food and the environment for and Orr holds a Bachelor of Arts in politics from New York University, and a Masters of Arts in government from Georgetown University.