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It seems like a simple question.
Though a vague answer is fairly easy to come up with, let’s take a look at why grass seed takes different amounts of time to sprout, spread and become a lovely, lush lawn.
How the Weather Affects Germination
The first thing to figure out is whether the seed you want to plant is from a cool or warm season grass. The conditions at different times of the year will allow some seeds to germinate while others won’t.
Cool season grasses, such as bluegrass, germinate best in the fall and spring, when the soil temperature is cool but not cold. These grass species are C3 plants, so higher summer temperatures cause these plants to lose too much moisture through transpiration, making them die back.
Warm season grasses, such as buffalo grass or bermuda, germinate best in late spring, with higher soil temperatures. As C4 plants, they thrive in the higher summer temperatures and don’t well with the lower temperatures of spring and fall.
Other climate issues that can change how long it takes for grass seed to grow include moisture and sunlight.
Excessive or insufficient moisture, either in the form of irrigation or rainfall, can slow or prevent germination by either drying out or drowning the grass seed.
Why Different Species of Grass Take Longer to Grow
I bet you thought that was it!
But there’s more involved in figuring out how long it grass seed take to grow!
Let’s see what the difference is between cool and warm season grass seed germination times:
- Cool season grasses tend to take two trends. Some species have evolved to germinate very quickly (5-15 days) during warm spells and establish themselves, like rye grass and fescue. Other species, like bluegrass, germinate slowly (20-30 days) because of the cool temperatures.
- Warm season grasses tend to take longer to germinate as a whole, between 10 and 30 days. Differing temperatures during spring are responsible for the greater variation in germination time for warm season grasses.
You learn more about warm and cool season grass seed types here: https://obsessedlawn.com/best-grass-seed-reviews/
Why Your Soil Condition Can Change Germination and Grass Growth Rates
The type and condition of your soil can change germination rates as well.
Both soil temperature and moisture can affect how quickly the seed germinates. Let’s take a look at the different soil extremes first:
- Clay soil tends to heat up slowly in the spring and holds water well. If you have light rain in the spring, you may still have a delay in germination because the soil temperature is cooler than the soils.
If you have heavy rains in the spring, the excess moisture can prevent the seed from being able to exchange gasses, lowering your germination rates.
- Sandy soil heats up quickly in the spring, but doesn’t hold water as well.
If you have moderate to even heavy rains, your seed will germinate more quickly as the soil heats up, but light rains may not keep enough moisture in the soil to allow germination, or may not provide enough moisture to maintain the young seedlings.
Other soil conditions that can alter germination speed and rate include pH; somewhat acidic soils can speed the germination process by causing scarification of the seed coat, which allows the seedling to break through the seed coat more quickly.
Extreme high pH (beyond 6-8) can cause problems with seedling growth by causing damage to the seedling or binding up certain nutrients, preventing the plant from growing properly.
But what about after the seed germinates? The same factors that can affect how the seed germinates can also cause differences in plant growth. A moderate approach to your lawn management practices will give you the best results, giving you a beautiful lawn to enjoy for years.
This should have given you some more ideas on figuring out some of the ins and outs of grass seed germination.