How To Plant And Grow Cool-Season Grass Seed

Your lawn will only live up to your expectations if the seed gets the right start. When it comes to planting and growing cool-season grass seed, that means following the right timing and conditions. It grows best when your soil temperature is between 50 and 65 degrees Fahrenheit. Once the timing is right, your job is to make sure the seed has good contact with the soil and stick to a steady watering routine.

If your approach has been tossing seed on bare spots and hoping for the best, you already know the result: patchy growth, weeds spreading faster than grass, and wasted effort. Or maybe you've avoided seeding altogether, assuming it's complicated. And if you've been tempted to try planting cool-season grass in summer, it's best to hold of, since these grasses thrive only when you match them to their natural rhythm. With a little prep, the seeds will grow into a thick, lush lawn.

The best time to plant cool-season grass is during early fall, from September till October, when soil temperatures are just right. If you miss that window, you can also seed in March or April, but during that time, there'll be more weed attacks. Before you spread your seeds, check your soil. Cool-season grasses prefer a soil pH from 6.0 to 6.8. Anything outside that range can stress your lawn and even turn it yellow-green. You'll also want your soil to have 5 to 20% organic matter. If your soil is lacking, you can add organic fertilizers to boost its concentration.

Once your soil is ready, it's time to seed. Spread the first batch in one direction, and the second at a right angle to avoid bare spots. You can improve the germination process by raking the area so that the seeds are in contact with the soil. To lock in moisture, cover the seeded area with one to two bales of straw per 1,000 ft². It's also important to know how often you should water your seedlings. Aim for about a ½ inch, and follow this routine until your grass is about 4 inches tall. You'll want to resist the urge to pull up the straw once the seeds pop, as it will break down naturally.

Once your cool-season grass seeds start sprouting, you can ease up on the watering schedule. Instead of frequent light watering, switch to deep watering, as it will help the roots to grow deeper into the soil. Follow the right length to mow your lawn by sticking to the one-third rule. Meaning, never cut off more than one-third of the grass blade at a time. If you cut too short, it can stress young grass and slow its growth. For those first few mowings, use a sharp mower blade so you don't tear or damage your seedlings. 

Make sure the soil is dry before mowing, as wet soil can leave ruts and footprints, which your young lawn definitely doesn't need. A good rule of thumb is to keep your grass on the taller side. Weeds are another challenge you'll want to get ahead of. A pre-emergent herbicide with siduron (often sold as "starter herbicide") is safe to use before, during, and even after your grass is growing. If weeds show up later, once your lawn has been mowed at least two times, you can switch to a post-emergent herbicide. And for those random individual weeds, try the simple "point and squirt" method so that you don't stress the rest of your grass.