Grass Seed Germination Temperature

Grass seed germination depends on the soil temperature, not air temperature. Cool season grasses germinate best between 50-65°F, with root development possible as low as 40°F. Warm season grasses need soil temperatures of 60-65°F to germinate, with peak leaf growth at 80-95°F. It's best to plant warm season grass in late spring and cool season grass in the fall. Other factors like sunlight, day length, and moisture also affect germination. Keeping the soil moist is crucial, but excess water can hinder germination. Plant grass seed when the soil temperature aligns with optimal temperatures for fastest germination. 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 degrees Fahrenheit. However, root development may tolerate temperatures to as low as 40 degrees Fahrenheit. Cool season grasses also go dormant where temperatures are above 90 degrees Fahrenheit. Warm season grasses need soil temperatures between 60 degrees and 65 degrees Fahrenheit to 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. 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? Air temperature versus 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. Daytime and night temperatures can vary considerably whereas the soils 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 fall 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. Warm season grass should be planted in warmer climatic conditions. They begin to germinate and show root activity when temperatures reach 60 degrees Fahrenheit to 65 degrees Fahrenheit. Below this temperature, the grass remains dormant and the seeds won't germinate. Its peak growing temperature for leaf growth is between 80 degrees to 95 degrees Fahrenheit. 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 degrees to 75 degrees Fahrenheit. The grass then 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 degrees to 45 degrees Fahrenheit, although the optimum temperature range for leaf growth is between 65 degrees to 75 degrees Fahrenheit. However, cool season grasses struggle in warmer temperatures. Once the temperature exceeds 75 degrees Fahrenheit growth slows down with it becoming dormant when temperatures exceed 90 degrees Fahrenheit. In terms of planting cool season grass varieties, the best germination time is between 50 degrees Fahrenheit to 65 degrees Fahrenheit. 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 degrees Fahrenheit to give the grass enough time to establish itself as grass seedlings are vulnerable to frost and freezing weather. Grass seedlings can grow in the winter months and fall is the best time to plant grass seedlings. 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 degrees to 70 degrees Fahrenheit 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 day lengths could impact on warm season grass seedlings growth. Other factors that affect germination. Temperature is just one of a number of factors that affect germination. Whilst warm soil is a prerequisite of germination other factors such as sunlight, day lengths 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 seed rotting. Summary. What is the right grass seed germination temperature? As we have seen it is soil temperature and not their 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 degrees Fahrenheit but they germinate at the fastest rate between 50 degrees Fahrenheit and 65 degrees Fahrenheit. Warm season grass seeds on the other hand need the soil temperature to be at least 60 degrees Fahrenheit to germinate but germinate at their fastest rate when the temperature is between 65 degrees to 75 degrees Fahrenheit. 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.