soil temperatures

Soil Temperatures in Your Georgia Garden

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Soil Temperatures in Your Georgia Garden

With the recent warm temperatures it is easy to be seduced into planting your summer crops now.  It is tempting to plant our vegetable transplants and seeds; we can’t wait for that first juicy tomato are a crunch pepper!  Be aware that soil temperatures are very important for success with your early summer plantings.

Soil Temperatures in Your Georgia Garden
Pepper Seedlings

Soil temperatures need to be 60-65 degrees F and rising at the 4 inch soil depth before you plant your summer crops.

If you install a transplant too early the roots won’t grow and the plant will just be sitting in the soil.  If we have a large amount of rain, which seems to be the norm this year, your new plant will just be sitting in wet soil.  This could mean early disease issues.

This morning the Blairsville weather station, near my home, indicated a 4-inch soil temperature of 44.1 degrees F. Dallas reported a 4-inch temperature of 47.2. In Griffin the 4-inch soil temperature was 50.9 degrees F while Tifton reported 56.3 degrees F. It is too early to think about tomatoes and peppers!

If the soil temperatures are not warm enough for seed germination, early seed plantings could rot.

The roots need to be actively growing to absorb water and nutrients.

If we plant and fertilizer summer vegetables too early we will be wasting fertilizer.  The plant roots simply can’t absorb it.  This fertilizer could get washed away, wasting your time and money. Also, this leached fertilizer could be problematic for our watersheds.

Determine your soil temperatures.

To determine your soil temperature at the 4 inch depth visit www.georgiaweather.net.  Click on the station nearest your garden.  Or, you can see a summary of soil temperatures across the state.

Soil Temperatures in Your Georgia Garden
Tomatoes planted last year AFTER the soil temperatures warmed up. Waiting until the soil temperatures are warm enough is one step to success for your summer garden.

Remember the rule of thumb is play it safe and wait!

Happy Gardening!

The Importance of Soil Temperatures in Your Garden

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It is the time of year when Georgia gardeners think about their Fall, cool-season gardens.   Leafy greens like spinach, leaf lettuce, and kale are all popular cool-season crops.  They don’t require the time necessary to make a “head”, you can eat the thinnings, and the varieties available are endless.

The Importance of Soil Temperatures in August
Lettuce in the Trustees Garden Savannah, Georgia

Often at the beginning of cool-season planting time, germination rates can be an issue.  “I have purchased new spinach seed and my germination rate is only about 50%.”  Or, “My arugula just did not come up at all.”  The problem might not be the seed quality but the soil temperatures, especially in a hot summer like we have been experiencing.  Seeds require a specific range of soil temperatures for best germination.

This chart from Cornell University shows optimum soil temperatures for germination of popular cool-season crops:

Crop Soil Temperatures needed for Germination Comments
Arugula 40 – 55° F May fail to germinate in warm soils
Lettuce 40 – 85° F Best germination below 70° F
Spinach 45 – 75° F May fail to germinate in warm soils
Kale 45 – 85°F
Collard Greens 45 – 85°F
Mustard Greens 45 – 85°F

If soil temperatures are close to the range extremes, the germination rate will definitely be affected.  These temperatures not only affect the germination rate but how quickly the seeds emerge.  For example, at 50°F spinach seed can take as much as three weeks to emerge.  At 70°F you could see emergence in just days.

Here are soil temperatures being reported by the University of Georgia Weather Network as of Tuesday, August 30th at 9:30 a.m.

Location Soil Temperature at 2″ depth
Ellijay  73.5 °F
Dallas  79.6 °F
Jonesboro  77.3 °F
Statesboro  83.0 °F
Tifton  78.9 °F
Valdosta  80.4 °F

Using the information shown, gardeners will have a difficult time growing spinach at this time in most parts of Georgia.

The lesson, be patient and monitor your soil temperatures.  Cool conditions are coming, I promise!

Happy Gardening!

Soil Temperatures Important in the Georgia Vegetable Garden-A Guest Post by Sharon Dowdy

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The air temperatures may be warm but the soil temperatures are still cool.
The air temperatures may be warm but the soil temperatures are still cool.

Georgia’s recent warm daytime temperatures have home gardeners itching to dig in the soil and plant summer crops. But University of Georgia experts warn gardeners not to be tempted. Soil temperatures are still far too low for seeds to germinate and transplants to survive.

“In Georgia, we may have a warm front come in one day and a cold front a few days later,” said Bob Westerfield, a consumer horticulturist with UGA Cooperative Extension. “It may hit 75 degrees outside, but the air temperature isn’t important when it comes to gardening – the soil temperature is.”

“That soil’s not ready for tomatoes. Summer crops need from 60 to 65 degrees.” he said.

Green beans can handle temperatures of about 55 degrees, but it is still not quite warm enough for them. If gardeners ignore his advice and seed their gardens, he says the seeds won’t germinate.

Gardeners who cannot resist the temptation can still plant cold season crops like asparagus, beets, broccoli, carrots, cauliflower, collards, kale, lettuce, mustard, onions, peas, potatoes, radish, spinach and turnips.

To track the soil temperatures in your area of the state, Westerfield recommends two different strategies. Buy a soil thermometer or use a meat thermometer to test the soil in your garden plot or rely on UGA’s Georgia Automated Environmental Monitoring Network at www.georgiaweather.net.

Soil temperatures “creep up slowly” and Georgia soils should be ready to sow in seed by early-to-mid

Use www.georgiaweather.net to check soil temperatures in your area. The current soil temperatures in Griffin are in the 40s.
Use www.georgiaweather.net to check soil temperatures in your area. The current soil temperatures in Griffin are in the 40s.

April, Westerfield said.

“And don’t be swayed by the vegetable transplants lining the garden center shelves,” he said. “Just because plants are in the stores doesn’t mean it’s time to plant them.”  Contact your local UGA Extension Agent for more information.

For more information on vegetable gardening in Georgia, see the UGA Extension publication, “Vegetable Gardening in Georgia”.

Sharon Dowdy is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.  Growing her own tomatoes has been beneficial for Sharon’s heart. She met her beau five years ago while buying tomato stakes at Home Depot.

Happy gardening!