Everything You Need To Know About Grass Seed Germination

Like most seeds, you’ll notice that grass seeds are very dry. They contain about 10% water, and when grass seed is stored, it can gain or lose a little water and, therefore, weight depending on the humidity. 

What Grass Seed Needs to Germinate

Your grass seed needs:

• Good seed-to-soil contact
• Even distribution
• Constant moisture
• Warmth is also crucial; the soil temperature should be at least 10°C.

Grass Seed Germination

To germinate, the seed must absorb sufficient water to soften the outer husk and flush out the enzymes that keep it dormant in a temperature range that allows germination, usually 10 to 15 degrees, depending on the seed type. 

When seeding, you are advised to water the grass seed frequently. This keeps the seed constantly wet for 24-48 hours to flush out inhibiting enzymes. If this is not done correctly and the seed dries between waterings, it returns to its dormant state. You can water this way for weeks, and nothing will happen. The secret is to water lightly and often so the seed does not dry out. In dry conditions, this can be quite a task.

How Long Does Grass Take To Germinate

Once that stage is complete, perhaps 24 to 48 hours, more enzymes are activated to enable the seed to utilise stored food and germinate. This is also when oxygen starts to be needed. A small root shoot will then emerge, which must contact moist aerated soil to develop into a grass plant. 

With one very shallow root, the seedling is delicate at this stage, so a constant water supply is needed. If not, the root shoot may wither and die, so this is a critical few days. Within 10-21 days, depending on temperature and seed mixture, leaves will have appeared, and the grass plant will start to photosynthesise and develop more roots. 

So, the first three weeks mean you must take great care to give the seedling the best start.

Temperature for Germinating Grass Seed

A bag of grass seed is a mixture of different grass seed types. These different grasses germinate at different temperatures, so if you plant when the temperature is only 10 degrees, half your seedlings may not germinate. Aim for at least 12 degrees soil temperature when seeding.

If you want to know exactly what your seed mixture will need in terms of temperature, once you’ve decided what grass seed you need from the Lawnsmith Shop, look at the various seed varieties that make up the mixture. Then, go to Grass Seed and Lawn Seed Mixtures and check the germination temperature for each seed in your mixture.

If you cover the lawn with polythene, you can seed and germinate in slightly cooler temperatures. This creates a greenhouse effect, warming the soil by one or two degrees.

Calculating Soil Temperature

A thermometer a couple of inches below the soil surface is the best way to get a soil temperature reading, but who can do that? So, to get a rough idea of soil temperature, the average day and night air temperatures. Therefore, frosty nights are zero, and sunny days maybe 16. The average is eight and, hence, still a little too cold! Also, consider the medium-term weather forecast because your seed will take 10-14 days to get going.