How Often To Water Grass Seed And How Long

To germinate and grow, seeds require water and a certain temperature range. 

Whether you are seeding your lawn from scratch, overseeding an existing lawn, or reseeding a problem spot in your yard, once the seeds are spread, and the germination process has begun, it’s critical to keep them moist at all times. 

You only get one chance to get it right because the germinating seeds and tiny sprouts will die if allowed to dry out. 

So how often and for how long will you need to water your grass seeds?

On average, water grass seed twice for 5-10 minutes a day to keep the seeds moist until they germinate. Germination takes from 5-30 days, depending on grass type and conditions, but remember, not all seeds will sprout simultaneously. Keep the seeds and soil constantly moist until all seeds have germinated.

Keep reading to find out how your grass type and other conditions will affect your ideal watering schedule when growing grass from seed.

how often to water grass seed

Lawn Preparation

If you are planting your lawn from scratch, water the ground generously (6-8″ inches of water) for several days before spreading your new seed.

If you are seeding an existing lawn, also water deeply several days before you seed. 

Before seeding, mow the lawn a little lower than usual and collect the lawn clippings so the new seeds can reach the soil. 

If you add soil or compost to the lawn area, do it before planting the new seed. 

This allows you to lightly rake the seed in instead of smothering the seed under too much loose soil.

Before or several days after seeding, apply a starter fertilizer that is high in potassium and phosphorus to your seeded area.

Because phosphorus is relatively immovable in the soil, applying a starter fertilizer will ensure a generous supply of phosphorus is within reach of the young seedlings, giving them a good jump start by promoting strong root development.

How Often To Water Grass Seed?

Grass seeds normally need water twice daily to stay constantly moist, but this will depend on your soil type and conditions. You may need to water 3-4 times daily for sandy soils and hot, dry weather to keep the seeds moist. For clay soils and wet weather, you may not need water at all.

After spreading your seeds, rake them into the top soil layer or cover them with 1/4″ inches of mulch to protect them. 

Rinse immediately with enough water to moisten the seeds and the top few inches of soil. 

The goal is to wet the seeds and moisten the soil without flooding. 

Continue to water the seeds 2-4 times per day, just long enough to keep the seeds and the top 2″ inches of soil moist until all the seeds have germinated.

If you reseeded your existing lawn, give it an occasional deep watering to maintain its health. 

Your established grass will help the new seed remain in place, as well as slow down evaporation and keep the soil shaded.

The best times of day to water are early in the morning when dew is still present and towards the middle of the day. 

Avoid watering very late in the evening or at night because the water will not evaporate properly, and the ground will stay damp.

If it is very hot and dry and you need to do a third or even fourth watering, ensure you are finished by late afternoon/early evening before the sun sets.

Once all of the seed has sprouted, continue to water lightly 2-4 times a day, depending on your soil and weather conditions.

Until the planted area shows dense green growth, don’t allow it to dry out; there may still be seeds that haven’t yet germinated. 

Keep an eye out for weeds even at this early stage.

How Long To Water Grass Seed?

On average, 5-10 minutes per watering is needed for the grass seeds and top 2″ inches of soil to stay moist. The length of time will depend on your soil type and weather conditions. For sandy soil and hot, dry weather, you may need to water for up to 15-20 minutes. For clay soils, 3-5 minutes may be enough.

If you are using an automatic sprinkler system, set your automatic timer. 

Make sure the number of minutes of sprinkler time allows you to maintain moist soil but nothing more.

If you don’t have high-quality sprinklers, inaccurate timers or poor water distribution could leave parts of the soil soggy and parts too dry.

If you’re going to the trouble of paying the cost for seed, then buying and spreading it, replacing your cheap lawn sprinkler may be worth it.

It will also help you maintain a healthy lawn in the long run.

If you are watering by hand using the garden hose and sprayer, be consistent with your timing and apply water evenly. 

Take care not to walk over the seeded areas leaving deep footprints. 

You will compress or compact the soil and potentially damage the sprouting seeds.

For small areas, for example, if you are patching a bare or thin spot, water by hand to keep the new seed moist and leave the remainder of the lawn on its normal watering schedule.

After the seedlings begin to grow, gradually increase the length of the morning watering session while decreasing the afternoon/early evening watering. 

Eventually, you’ll want to water between 6 and 10 am when the weather is cool.

How Long Does It Take Grass Seed To Germinate?

Germination takes anywhere from 5-30 days, depending on your grass type and conditions. Not all seeds of the same grass type will germinate simultaneously due to differences in their location in the soil, as well as their quality, maturity, and the rate they are absorbing water.

Under ideal conditions, the table below shows the optimum temperature range and average germination time for different warm-season and cool-season grass varieties.

Name Of GrassType Of GrassType Of Grass/TemperatureGermination Time
Kentucky BluegrassCool-season50°-65° degrees Fahrenheit (18° C)14-30 days
Annual RyegrassCool-season60°-75° degrees Fahrenheit (24° C)5-10 days
Perennial RyegrassCool-season50°-65° degrees Fahrenheit (18° C)5-7 days
Red FescueCool-season50°-65° degrees Fahrenheit (18° C)12-22 days
Tall FescueCool-season60°-65° degrees Fahrenheit (18° C)7-12 days
BahiaWarm-season85°-95° degrees Fahrenheit (35° C)28 days
BermudagrassWarm-season70°-95° degrees Fahrenheit (35° C)7-14 days
BuffaloWarm-season70°-90° degrees Fahrenheit (32° C)15-21 days
CentipedeWarm-seasonOver 70° degrees Fahrenheit (21° C)10-28 days
St. Augustine* (plug)Warm-seasonN/A*7-14 days
ZoysiaWarm-seasonOver 80° degrees Fahrenheit (27° C)14-21 days

* St. Augustine grass does not usually produce viable seeds; it must be established using sod or plugs.

Plant warm-season grasses in spring and plant cool-season grasses early in the fall. 

Keep in mind the germination times given in the table are for optimum conditions.

In cooler temperatures, the seeds are likely to take longer to germinate, which means you will be watering for a longer period than the germination times indicated in the table. 

In addition, many seed brands sell mixtures or blends of multiple grass types, each of which will have different characteristics which affect their development and hence their germination time.

Check the grass seed package to find out what grass varieties are in the seed mix. 

Knowing what grass types are present in the mix will better predict the total germination time.

For these reasons, it’s important to keep watering 2-3 times per day to keep the top 2″ inches of soil and any mulch surrounding the seeds moist until you are confident all the seeds have germinated.

To help your lawn more, check out our favorite ways to make grass grow green and thick.

Can You Overwater Grass Seed?

Overwatering is bad for grass seed. Overwatering often results in poorer germination rates, and the seeds can float or wash away, leading to uneven distribution. Overly-wet soil may also result in fungal growth, causing the breakdown and decomposition of grass seeds that haven’t germinated.

Keep an eye out for pooling water. 

It’s a sure sign you are overwatering your grass seed, which can lead to several problems.

Waterlogged grass seed often germinates poorly and can rot and die. 

If you see your seeds are soaked, stop watering until the excess water has evaporated.

After that, cut back on the frequency and amount of time you water, so the topsoil and seeds remain moist but do not become waterlogged.

Overwatering also leads to soil shifting. 

Your seeds may end up buried and die instead of germinating because they are not receiving any sunlight.

In addition, if overwatered seeds can become unevenly distributed or wash away, so you will end up with clumpy growth.

Once all of the tiny grass seedlings have appeared, continue to water 2-4 times a day (depending on your soil and conditions) but be careful not to overwater – allow the soil to dry slightly between each watering.

Overwatering can drown the new grass seedlings by preventing the roots from getting oxygen, and soil

Persistent wetness at this stage can lead to serious root diseases, which may even kill the new grassroots.

Once established, your new green lawn will typically require about 1″ inch of water per week, including rainfall.

Deep watering should be done one or two times per week once rather than light watering daily to encourage deep root growth.

Some sources even recommend leaving sufficient time between waterings for the grass to start showing some signs of stress because this will train the roots to grow much deeper into the soil to reach available water and nutrients.