Optimal Seed Germination Temperatures By Variety

An administrator from another program once commented that running the Edible Learning Lab was “just watering plants”.  Sure.  That’s all there is to this process.

For those with even a little experience with the growing process, it’s clear that there is far more to the food production process that just a few simple steps.  Now that said, most of the steps are simple once you understand the interrelationships that each step shares with the others.

Seed germination is dead simple if you have the right conditions.  Moisture, temperature, and in some cases light, is all that is required to force seeds out of the dormant state.  But how do you know what the right temperature is?  Of the proper moisture for that matter?  Smart science nerds have already figured that out and we are very grateful for that!

The first step is to identify the ideal temperature that each variety requires for effective germination.  You can reference the post below to find the optimal temperature for most common garden varieties.

Once you have identified your optimal temperature for germination you need to measure the soil temperature to determine what you have to work with and the adjustments you may need to make.  This technique is valuable for broadcast seeding or row seeding in the garden, high tunnel, or raised planters.  The same can be applied to the seed starting station where controlling the soil temperature can be much easier using lights and propagation mats.

Here’s how you measure the soil temperature:

• For cool-season crops, measure at a depth of 2”
• For warm-season crops, measure at a depth of 4”
• When using a bubble thermometer (made of glass), use a dowel to create the hole at the proper depth and then insert the thermometer into the formed hole.
• Digital probes and thermometers with metal probes can be inserted directly into the soil

TIP: Be sure to test your thermometer by comparing its reading with that of a second thermometer.  Simply hold each in the air for 60 seconds and then compare for accuracy.

Temperature has an impact on germination beyond just triggering the process.  The optimal temperature is that which allows for the MOST seeds to germinate in the LEAST amount of time.

Optimal Temperature for Germination

The ag department at the University of Arizona has charted the optimal temperatures for the most common vegetable and herb varieties.  Use this chart to find the optimal temperature for your varieties.  Once you have identified the optimal temperature, be sure that you properly measure the soil temperature in your garden bed and plant when optimal.