How Soil Temperature Affects Seed Germination, Seedlings and Garden Plant Production

Hardy and very hardy vegetable seeds;

The thing master gardeners know and understand all too well. Hearty and very hardy vegetable seeds generally germinate best in a soil temperature of sixty-five degrees F, or eighteen point three degrees C. These hearty to very hearty vegetable plants grow best in soil temperatures at about sixty degrees F. or fifteen point six degrees C. during the daylight hours, and forty-five degrees F. or seven point two degrees C. at night.

Here is a little fun fact you may not be aware of; Favored by generations of master vegetable gardeners, Hardy vegetable plants such as cabbage, broccoli, Brussels sprouts, carrots, kale, leeks, rutabagas, and turnips not only survive temperatures as low as 20 degrees F. before succumbing to the cold. Their flavor and texture actually improve during periods of cold weather. Further adding to their allure, after thawing out, these hardy vegetables more often than not actually continue growing as things warm up between periods of freezing cold weather.

Tender and very tender vegetables;

Tender and very tender vegetable plant seeds germinate best in soil temperatures, eighty to ninety degrees F, or twenty-six point seven to thirty two point two degrees C. These tender to very tender vegetables grow best in soil temperatures in the seventy-five to eighty-five F, range or twenty-three point three to twenty nine point three degrees C. by day, and fifty-five degrees to sixty-five degrees F, or twelve point eight degrees to eighteen point three degrees C. by night.

Vegetable plants like Cantaloupe and Melons, Eggplant, Lima Beans, Okra, jalapeno or bell Peppers, sugar pie Pumpkins and Winter Squash, and Roma or Early Girl Tomatoes do not like cold weather earning them the distinction of tender vegetable plants.

These soil temperature ranges are important, growing vegetables from seeds indoors at a constant seventy degrees or twenty-one point one degrees C. both day and night produces week seedlings. By day, this temperature is too low for tender and very tender vegetables and too high for all vegetable plants at night.

High temperatures at night produce seedlings with tall week stems and small leaves, temperatures too low and the seedlings will suffer worse wither and die.

In order to avoid these conditions, consider using the combination of plant or grow lights, and heating pads designed especially to maintain the proper daytime and nighttime growing temperatures and an easy to use Chaney soil thermometer.   

As a still wet behind the ears newbie gardener, or a wrinkled ole master vegetable gardener we all have one thing in common. We do not want to waste time and money on seeds, seedlings or hothouse vegetable plants that do not survive and produce tasty fruits and veggies. What we do want to do, before we plant anything, first ask ourselves this one simple question. What is best Soil Temperature and how does it affect seedlings and garden plants? From there we will make better what, where and when to plant decisions.

 Happy gardening, Mike