How soil temperature affects grass growth

By | 24/11/2017
New Grass

The soil temperature in which your grass lives greatly affects the speed at which the grass grows.

A warmer soil contains more energy. More energy available enables chemical process driving plant growth to work faster and more efficiently. This means grass can make food quicker (through photosynthesis) and therefore grow faster. There is a direct correlation between the temperature of the soil and the speed in which grass grows.

One of the main chemicals to cool season grass health is water. If the soil is cold or frozen, water cannot move through the grass plant easily and so growth slows or even stops. Conversely, if the soil is too hot, water is lost too quickly through evaporation. This dries out the plant and its growth also slows.

The optimum range of soil temperature for cool season grasses is between 18-24 degrees Celsius. Grass will still grow outside of this range, just not as quickly.

Different processes in the plant are activated at different temperatures. This table shows the soil temperatures which are needed to maintain good grass growth.

Table of grass growth rates in different temperatures

Soil TemperatureGrass growth patternResult
1 °CRoot growth stopsCold stress
5 °CShoot growth stopsCold stress
18-20 °COptimum for grass rootsIdeal temperature
15-24 °COptimum for grass shootsIdeal temperature
25 °CRoot growth stopsHeat stress
32 °CShoot growth stopsHeat stress
Table of soil temperatures on grass growth

Soil temperature is not the same as air temperature

Soil temperature is not the same as air temperature. The earth acts like a giant radiator. It gradually absorbs the suns energy over time, and then releases it slowly. Air temperature can fluctuate dramatically as day turns to night and as the seasons progress. Soil takes a long time to change temperature.

In the spring, the soil is cold from the winter and can take a long time to heat up. This is why spring scarification and lawn repairing can pose problems due to the soil not having warmed sufficiently. Seed may not germinate quickly and grass growth can be sluggish.

Using an infra red soil thermometer to check soil temperature
Using an infra red thermometer to check soil temperature

In the autumn, the opposite is true. The air temperature maybe falling, but the soil retains a lot of heat. This helps seed germination and aids the grass in absorbing valuable nutrients from autumn fertilisation. Many lawns can continue to look green and lush well into autumn and early winter. Autumn is usually the best time for seeding and major lawn renovation work.

If you want to know how your grass is coping with the current climate in your then buy yourself a soil thermometer. Knowing the temperature of your soil will really help you provide the correct treatment for your grass at the right time.

A lawn in autumn
Autumn is the best time for lawn repairs as the soil is usually quite warm.

6 thoughts on “How soil temperature affects grass growth

  1. Doug

    Slightly related here, from my experience as a gardener, if you spill petrol on the grass – set it alight it asap. Obviously you will scorch the sward, but it you leave it the grass will die back for months, if you burn it off the grass recovers much faster.

    1. Kris Lord Post author

      Hi Doug, Yes, that would make sense. You would be burning off the petrol, but leaving the roots intact under the insulating soil. The grass would recover, as long as not petrol much has seeped in!

    1. Kris Lord Post author

      I’m sorry, I don’t really understand the point of your question?
      Petrol is obviously terrible for all plants all year round.
      The only way it should be used in horticulture is for powering machinery.

    2. Anthony kelham

      Cannot believe you ask such a stupid question are you human


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