Grass Seed Germination Temperature: Air Temperature Vs Soil Temperature

Keith Hardy - Bio Photo
Keith Hardy
Senior Editor

Keith has been involved in the gardening and landscaping industry for the past 21 years. From a jobbing gardener to running his own landscaping services....

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Achieving that perfect lawn starts at the very beginning—with the germination of your grass seeds. But here’s the catch: not all seeds are created equal, and neither are the conditions in which they thrive. One of the most critical factors that can make or break your lawn’s success is grass seed germination temperature.

As a seasoned lawn care expert with years of hands-on experience, I can’t stress enough how vital it is to understand the optimal soil temperature for your chosen grass type. Whether you’re planting cool-season grasses like Kentucky Bluegrass or warm-season varieties like Bermuda, the temperature of the soil can significantly impact how well your seeds germinate. Get it right, and you’re on your way to a lawn that not only looks good but is also resilient and low-maintenance. Get it wrong, and you could be facing a season of patchy, uneven growth, or worse, seed failure.

Below, we will examine the science behind soil temperature, its impact on seed viability, and practical tips to measure and optimize it. By the end, you’ll have the in-depth knowledge needed to give your grass seeds the best start possible, setting the stage for a lawn you’ll be proud to show off.

Why Knowing Grass Seed Germination Temperature Is Essential

When planting grass seed it is important to know that if the temperature is too cold or too hot the seed will fail to germinate or to germinate properly. So, what is the right grass seed germination temperature?

This will largely depend on the type and variety of grass seed that you are growing. Some grass varieties only grow in warmer temperatures and these are known as warm-season grasses. Other varieties grow in much cooler conditions and won’t grow below and above certain temperatures and these are known as cool-season grasses.

If you’re planting cool-season grass, the soil temperature should be above 45°F, however, root development may tolerate temperatures to as low as 40°F[1]. Cool-season grasses also go dormant where temperatures are above 90°F. Warm-season grasses need soil temperatures between 60° and 65°F to germinate.[2]

Optimal Grass Seed Germination Temperature Chart

When it comes to grass seed germination, knowing the optimal soil temperature for your specific grass type is crucial. This chart serves as a quick reference guide, helping you choose the right grass for your lawn based on soil temperature and the best planting season.

Grass TypeOptimal Soil Temperature (°F)Best Planting Season
Kentucky Bluegrass59-86Spring or Fall
Bermuda75-90Late Spring to Early Summer
Zoysia70-80Late Spring to Early Summer
Fine Fescue50-75Spring or Fall
Tall Fescue60-75Spring or Fall
St. Augustine65-80Late Spring to Early Summer
Bahia65-70Late Spring to Early Summer
Centipede70-85Late Spring to Early Summer
Buffalo Grass60-75Late Spring to Early Summer

At What Temperature Does Grass Seed Germinate

At What Temperature Does Grass Seed Germinate

Temperature is by far the most essential factor in determining grass seed germination. Grass seeds require the soil temperature to be within a certain range in order for germination to occur. This range depends on the type of grass seed that you are planting, either cool-season grass or warm-season grass.

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Air Temperature vs Soil Temperature

When we talk about the temperature it is important not to get confused with air temperature. Whilst the daytime temperature impacts the temperature of the soil, the soil itself retains heat far longer than the air does.[4] Daytime and night temperatures can vary considerably whereas the soil’s temperature will remain fairly constant. 

It is also significant to note that soil temperature can take time to catch up to that of air. If you have had a cold spell and the daytime temperature suddenly increases, you will likely find that the ground temperature can be much colder. You could have a situation where there is a brief warm weather period, such as with a ‘false spring‘, where the soil will not become warm enough for the seed to germinate as expected as the soil is too cold. 

It is therefore not unusual to find the temperature of the soil is different from that of the air. So, whilst climatic temperature can give you an idea when it comes to planting grass seed it is best to determine the soil temperature using a soil thermometer.

Warm-Season Grasses

Grass Seed Germination Temperature

Warm-season grass should be planted in warmer climatic conditions. They begin to germinate and show root activity when temperatures reach 60°F to 65°F. Below this temperature, the grass remains dormant and the seeds won’t germinate. Its peak growing temperature for leaf growth is between 80° to 95°F

When it comes to planting warm-season grass, late spring is often considered the best time. You should look to plant when the soil temperature reaches 65° to 75°F. The grass should then be already established so that when the heat of summer arrives top growth can thrive fully establishing your lawn.

Cool-Season Grasses

Cool-season grasses thrive in more temperate conditions and can struggle in warmer climates. Root development can be triggered with temperatures as low as 40° to 45°F, although the optimum temperature range for leaf growth is between 65° to 75°F. 

However, cool-season grasses struggle in warmer temperatures. Once the temperature exceeds 75°F growth slows down, with it becoming dormant when temperatures exceed 90°F.

In terms of planting cool-season grass varieties, the best germination rates are achieved when temperatures range from 50°F to 65°F. Fall is often considered the best time to plant cool-season grasses. You need to leave a window where there are at least eight weeks before temperatures drop to below 45°F to give the grass enough time to establish itself as grass seedlings are vulnerable to frost and freezing weather.

Grass Seed Mixtures

grass seed mixtures for transitional zone

If you are in a transitional zone it is not uncommon to look to use grass seed mixtures to provide a better lawn that can adapt to transitional conditions. In terms of germinating the sweet spot would be between 60° to 70°F to ensure both the warm and cool season seeds can germinate in unison.

Spring is likely to meet this criterion best as this will allow the cool season grass to establish itself before the hot weather. Although it would also be possible to plant in late summer or early fall other criteria, such as daylengths[5], could impact on warm-season grass seedlings growth.

How to Measure Soil Temperature: A Step-by-Step Guide

The most reliable method is to use a soil thermometer. Below is a step-by-step guide to help you accurately measure soil temperature, ensuring your grass seeds have the best chance for successful germination.

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Tools You’ll Need

  • Soil thermometer
  • Garden trowel
  • Notepad or mobile device for recording measurements

Step 1: Choose the Right Time

The best time to measure soil temperature is in the early morning or late afternoon. These times provide the most consistent readings, avoiding the temperature fluctuations that can occur during the day.

Step 2: Select the Planting Area

Identify the area where you plan to sow your grass seeds. Make sure it’s a representative spot that captures the general condition of the entire planting area.

Step 3: Prepare the Soil

Use a garden trowel to loosen the soil in the selected area. Remove any debris, such as leaves or rocks, that might interfere with the thermometer’s accuracy.

Step 4: Insert the Soil Thermometer

Place the soil thermometer into the soil, ensuring it’s inserted at a depth of 3 to 4 inches. This depth is ideal for capturing the soil temperature where the seeds will actually germinate.

Step 5: Wait and Record

Leave the thermometer in place for at least three minutes to get an accurate reading. Once the time is up, check the thermometer and record the temperature in your notepad or mobile device.

Step 6: Take Multiple Readings

For larger areas, it’s advisable to take multiple readings at different spots to get an average soil temperature. This ensures that you’re accounting for any variations across the planting area.

Step 7: Analyze and Plan

Compare the recorded temperatures with the optimal germination temperature for your chosen grass type. If the soil temperature is within the ideal range, you’re good to go. If not, you may need to wait or take measures to modify the soil temperature.

If you are consistent in your method, you’ll gain a more precise understanding of your soil’s temperature, allowing you to make informed decisions for successful grass seed germination. In addition, by measuring the temperature regularly and keeping logs you will be able to build up a picture of temperature changes throughout the seasons, which will improve your lawn care maintenance practices.

Other Factors that Affect Germination

Temperature is just one of a number of factors that affect germination. Whilst warm soil is a pre-requisite of germination other factors such as sunlight, daylengths, and adequate moisture can determine the germination rate. 

It is temperature and moisture that trigger germination. Once you have planted your seed you must keep the soil moist so that they germinate. However, you have to ensure that your watering regime is on point as excess water, noticeable if water pools, can reduce germination rates through the seeds rotting. 

Case Studies: The Importance of Soil Temperature in Grass Seed Germination

Case Study 1: The Tale of Two Neighbors


Meet John and Sarah, neighbors who both decided to plant Kentucky Bluegrass in their front yards. John, an avid gardener, took the time to measure the soil temperature before planting. Sarah, on the other hand, planted her seeds based on the calendar, assuming spring was the perfect time.


John’s lawn turned out to be lush and vibrant, while Sarah’s experienced patchy growth. The difference? Soil temperature. John waited until the soil consistently hit the optimal germination temperature of 59-86°F, ensuring uniform germination. Sarah’s soil was cooler, leading to delayed germination and uneven growth.

Key Takeaway

Understanding and measuring soil temperature can lead to consistent and successful seed germination, saving both time and resources in the long run.

Case Study 2: The Community Park Project


A local community decided to revamp their park with a mix of cool-season and warm-season grasses. They hired two contractors: one who considered soil temperature and another who did not.


The area managed by the first contractor had robust growth, requiring less overseeding and maintenance. The second contractor’s area had bare spots and required additional resources for fertilization and overseeding.

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Key Takeaway

In large projects like community parks, ignoring soil temperature can lead to increased costs and labor in lawn maintenance.

Case Study 3: The Rookie Mistake


Tim, a rookie homeowner, decided to plant Zoysia grass, a warm-season variety. Ignoring advice on soil temperature, he planted the seeds in early spring when the nights were still cool.


Tim’s seeds experienced poor germination rates. Zoysia grass prefers soil temperatures between 70-80°F for optimal germination. Tim’s soil was well below this range, leading to seed wastage and a need for replanting.

Key Takeaway

For warm-season grasses like Zoysia, soil warmth is crucial. Planting without considering soil temperature can lead to wasted seeds and additional costs.

By examining these case studies, it becomes evident that soil temperature plays a pivotal role in the success of grass seed germination. Whether you’re a homeowner or a professional landscaper, understanding this vital factor can make the difference between a thriving lawn and a lackluster one.

Troubleshooting Guide: Solving Common Germination Problems

Even with the best preparations, you might encounter some hiccups along the way to achieving that perfect lawn. Don’t worry; you’re not alone. In this troubleshooting guide, we’ll address common issues like uneven germination and seed rot, offering practical solutions to get your lawn back on track.

Uneven Germination: A Patchy Problem


  • Sporadic patches of grass
  • Inconsistent growth across the lawn

Common Causes

  • Inconsistent Soil Temperature: Variations in soil temperature can lead to uneven germination.
  • Poor Seed Distribution: If seeds are not evenly spread, they won’t germinate uniformly.


  1. Recheck Soil Temperature: Use a soil thermometer to ensure consistent temperature across the lawn.
  2. Overseed: Apply additional seeds to the bare patches, ensuring even distribution.
  3. Level the Soil: Uneven soil can lead to temperature variations. Level it out for consistent germination.

Seed Rot: The Unseen Enemy


  • Foul smell from the soil
  • Seeds appear mushy and discolored

Common Causes

  • Overwatering: Excessive moisture creates a breeding ground for fungi.
  • Poor Drainage: Soil that doesn’t drain well can lead to waterlogged conditions.


  1. Adjust Watering Schedule: Reduce the frequency and amount of watering.
  2. Improve Drainage: Amend the soil with organic matter like compost to improve its drainage capabilities.
  3. Apply Fungicide: Use a lawn-safe fungicide to treat the affected area.

Additional Tips

  • Soil Testing: If you’re facing persistent issues, consider a comprehensive soil test to check for nutrient imbalances or pH levels that could be affecting germination.
  • Consult a Professional: For severe or recurring problems, it may be beneficial to consult a lawn care expert for a tailored solution.

Below is a chart that can serve as a quick reference guide to help you identify and solve common problems that may arise during the grass seed germination process. From uneven growth to seed rot, here’s how to tackle these issues head-on.

ProblemLikely CauseSolution
Uneven GerminationInconsistent Soil TemperatureRecheck soil temperature and level the soil for uniformity.
Poor Seed DistributionOverseed the bare patches, ensuring even distribution.
Seed RotOverwateringAdjust watering schedule to prevent excessive moisture.
Poor DrainageAmend soil with organic matter to improve drainage.
Slow GerminationLow Soil TemperatureWait for optimal soil temperature or consider soil warming techniques.
Old or Expired SeedsUse fresh seeds with a high germination rate.
Patchy GrowthInadequate SunlightTrim overhanging branches or consider relocating to a sunnier spot.
Nutrient DeficiencyConduct a soil test and amend soil as needed.
Seedlings DyingFungal DiseasesApply a lawn-safe fungicide and improve soil drainage.
Pest InfestationUse a lawn-safe pesticide and consider natural pest deterrents.

Wrap-Up: What Is the Right Grass Seed Germination Temperature?

As we have seen it is soil temperature and not air temperature that is important when it comes to the point at which grass seeds will germinate or remain dormant.  

Cool-season grass seeds will germinate at temperatures as low as 40°F but they germinate at the fastest rate between 50°F and 65°F. Warm season grass seeds,  on the other hand, need the soil temperature to be at least 60°F to germinate, but germinate at their fastest rate when the temperature is between 65° to 75°F.

Ultimately, the best time to plant grass seed is when the grass type lines up with the optimal temperatures for the fastest germination as it will allow grass seedlings will appear sooner and the lawn can be established faster.


  1. Pennsylvania State University, Peter Landschoot, Professor of Turfgrass Science: The Cool-Season Turfgrasses: Basic Structures, Growth and Development
  2. Oregon State University, Department of Crop and Soil Science: Cool-season or Warm-season Grasses
  3. Prudue University, Aaron J. Patton: A Guide to Establishing Seeded Zoysiagrass In the Transition Zone
  4. Pennsylvania State University, Jason Reed: Soil Temperature and Seed Germination
  5. Oregon State University, Department of Crop and Soil Science: Cool-season or Warm-season Grasses
Keith Hardy - Bio Photo
Keith HardySenior Editor

Keith has been involved in the gardening and landscaping industry for the past 21 years. From a jobbing gardener to running his own landscaping services. He is now dedicated to bringing you the latest in gardening news. Read more

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