How to Water Your Newly Seeded Grass Lawn: Best Practices and Common Mistakes

Planting new grass is a satisfying investment into your lawn. But many planters make a few common mistakes that can lead to disaster. In this guide, we’ll make sure your newly planted lawn gets off to a great start and grows in vibrantly.

Q&A has been installing lawns, grass, & sod in the Pittsburgh area for over 16 years. We do a ton of lawn installations in the South Hills every year.

How often should you water new grass seed?

Water daily for the first three weeks

The goal is to keep the soil moist at all times. So, try to water 2-3 times daily. The best times of day to water are in the morning or early evening when it is cooler to prevent the grass from burning in the hot sun.
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Larger patches of grass and whole lawns are typically watered best with a sprinkler or a combination of sprinklers. I recommend starting by running the sprinkler for 10-15 minutes in each area and adjusting as needed to avoid any puddling.  It is important to not over water and drown the new grass as that can kill the new grass and prevent germination.  Once you see the soil is no longer accepting the water, it is best to stop.
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If you can only water once a day, I’d recommend doing it in the morning. Avoid watering late in the day or at night, especially during humid periods of the year, you will increase the risk of the lawn catching a disease or fungus as it will not dry out overnight.

Pay attention to the soil; adjust to weather conditions

If it rains earlier in the day, check to see if the soil is dry enough to water later on. The coloring of the soil surface is a great indicator for whether the soil is drying out.  If you see that the area you watered is drying out by later in the day, another small watering session would go a long way.

If it’s been raining a lot and the soil has been staying wet, you don’t need to water as much. Just keep an eye on the ground. In periods of drought and intense heat, you may need to water 3 times in a day.

It’s been a few days. When will my grass start growing?

During optimal growing conditions, seeds will start to germinate and you will see little sprouts of grass within 7-10 days.  You will continue to see germination of seeds 3-4 weeks after the initial planting, so it’s important to be patient.  During cooler periods of the year when the temperatures are dropping into the 40s and 50s at night, seeds will take a little longer to germinate.

Note: It is important to continue to water daily until you see most of the area fill in.

After 3 weeks, reduce watering to twice a week

You can cut back to watering every other day or twice a week after the first month. Grass will still be filling in for the next month or two as the roots grow deeper. Once a healthy carpet of grass has grown in, you can water a little longer at a time and less frequently. Longer watering 2-3 times a week soaks the ground up to 6 inches deep, which promotes large, healthy root systems.

When can you cut/mow new grass?

The first cut varies based on growth but on average after 4-6 weeks is a safe bet. You want the grass to come in thick but cut it before it gets too tall and messy.

How to keep grass seed from washing away

Straw mats are the best option when it comes to preventing erosion on sloped ground. Lay an inch of straw over top of the newly seeded soil. Remove excess straw over the next week or 2 to prevent the straw matting down and blocking new growth.

Prevent puddles by not overwatering. Hydroseeding alternatively provides a sticky medium for the seeds to take root, and prevent washing away.

When can you remove straw/straw blanket?

We’d recommend removing the straw once it’s clear there is no new growth to come. Usually after 3-4 weeks, most of seeds that are going to sprout have already started.

Never abruptly change watering habits

If you water your new lawn every day for 2 months and it comes in perfect, then go on vacation for a week and it goes multiple days without water, your lawn will significantly suffer.  Your seeds get used to a certain amount of water on regular intervals, and they cannot handle a sudden change.

It’s crucial you use a close-eye when caring for your new grass and stick to a schedule.

Goldenrod

Goldenrod is a genus of flowering plants in the sunflower family. This group of plants is known for its showy yellow flowers that bloom in late summer and early fall. While often wrongly blamed for seasonal allergies, goldenrod is actually a valuable source of nectar for pollinators and has been used for medicinal purposes by Native Americans for centuries. There are over 100 species of goldenrod, many of which are native to North America.