Seeding a Lawn in September

With summer coming to an end, and the temperatures dropping, it’s time to think about reseeding your lawn. Mid-August through September is the best time to re-seed an existing lawn and fill in those bare spots and small areas of dead grass. 

For cool-season grasses, such as Kentucky Bluegrass, early to mid-September is the sweet spot, while warm-season grasses like Bermuda grass and Zoysia may prefer a mid-August to early September planting. As their names suggest, cool-season grass grows primarily in spring and fall while warm-season grasses thrive in the warmer temperatures of summer. 

The warm soils of  September, combined with soil moisture and cooler nights, will let the seed germinate as efficiently as possible. It will also give cool-season lawns a month or two to establish themselves before the first frost. 

Starting the task now will give you time to seed before the cold of late fall and early winter when new growth may be stunted by the cold. 

There are many different seeds to choose from when overseeding your lawn; the most popular include Kentucky Bluegrass, Perennial Ryegrass, Tall Fescue, Fine Fescue, and Bermuda grasses. Mixes of Kentucky Bluegrass and Perennial Ryegrass are good seed choices for our area. Lawn care for both species is similar and they have a good tolerance for our climate. 

Before you plant grass seed, be sure to prepare the soil. Remember that seed must come into contact with the ground in order to germinate, so if you are overseeding an existing lawn a thorough raking to de-thatch is recommended. For bare areas loosen the top layer of soil and test the pH. Most lawns grow best with soil that is slightly acidic to neutral (pH 6.2–7.0).  Your local garden center will have the additives you need to achieve this pH reading. 

After preparing your soil and spreading the seed, be sure to keep the top level of the soil damp at all times to give all of your seed an equal opportunity to grow. It is also recommended to use a seed starter fertilizer to help give the new grass shoots a jump start before the first frost sets in. 

After you have growth that has reached 2 inches you can now give it a trim. Don’t let new grass grow too long or it won’t develop a strong crown. 

Finally, don’t forget that while you can leave clippings on the lawn as an added fertilizer, you shouldn’t let fallen leaves lie in place as they will suffocate new growth!