Dr. Grow: Sowing seeds: Fall is best time to plant new grass seeds

A seed spreader can be used to distribute new grass seeds evenly over the ground.

When is the best time to overseed cool season grasses in my lawn?

If I've been asked this question once, I've been asked it thousands of times. Here is the answer:The best time to overseed cool season grasses is in the fall of the year.

In the heartland, I define the fall as the first of August to the middle of October. The earlier you can plant, the longer the new grass will have to get established before the onset of cold weather.

You plant cool season grasses (bluegrass, fescue, and rye) in the fall for three important reasons. First, seeds germinate faster when soils are warm, and they are warmer in the early fall than in any other season of the year. Second, cool season grasses grow better when temperatures are cool and soils are moist. New grass seedlings established in the early fall will be able to grow rapidly during the best grass-growing conditions of the year. If you seed in the spring, the weather after germination is usually hot and dry. Third, if you seed in the spring, crab grass germinates at the same time new grass seedlings are coming up. Because early summer is usually warm and dry, you have to water to keep new grass alive. This watering also promotes crab grass growth, which results in aggressive competition for new grass seedlings.

Now that I have convinced you to seed in the fall, let me describe an easy way to accomplish the task. First and foremost, remember that for best germination results, grass seed must be placed in the soil. Seed gets water for germination from the soil that surrounds it. Don't just throw seed on the top of the ground and assume that it will germinate. I can guarantee 95 percent of it won't.

How do you get seed into the ground without tilling up your existing lawn? First, spread your seed over the existing lawn. For blue grass, spread two to three pounds of seed per 1,000 square feet. For fescues and ryes, spread five to 10 pounds of seed per 1,000 square feet. Use the higher rates on areas of your lawn that are thin, and the lower rates on areas where some grass exists.

Next spread new lawn starter fertilizer on the ground. Don't use 12-12-12. Use one that is unbalanced, more phosphorous than nitrogen. Phosphorous encourages new root development.

Now run over the seeded area with a verticutter. Do this three times in three different directions. Most people will have to rent this machine. Let all of the grass debris lay on the ground. It will provide a mulch which will help moisture in the ground and aid in erosion control.

After using the verticutter, water your seeded area until the soil is soggy. Watch that you don't water much and cause soil erosion. After initially watering keep the soil constantly wet until germination occurs and the lawn has been mowed once or twice. The frequency of subsequent watering will be determined by wind and temperature conditions. You may have to water daily and sometimes twice a day to keep the top one inch of the soil from drying out. This is the most critical time during the seeding process. If you let the soil dry out, the newly emerging, very succulent grass plants may die.

Mow the new grass when it gets tall enough to mow. Mowing will enhance the maturing of the new grass seedlings. If the new grass is not mowed, it will fall over and disease will begin to invade and kill the new plants.

After the new grass has been mowed once, reduce watering to once or twice a week. Continue watering in the fall until rainfall occurs on a weekly basis and the daytime temperatures stay in the 60s and below.

You may think that you need to kill weeds first and then seed. If your lawn has weeds that are hard to control such as dallisgrass or Johnson grass, get rid of the weeds first using glyphosate. You can seed a week after you spray the herbicide. If you lawn has a lot of other miscellaneous weeds, don't be concerned. Seed right into the weeds. When you use the verticutter dormant weed seeds are brought to the surface and germinate along with the grass seed. Even if you had no weeds in your lawn before seeding, your new lawn will be full of weeds. Once the lawn is established with a good stand of grass, you can easily control weeds.

Finally fertilize your lawn about a month after germination. Be sure to use a high nitrogen, low phosphorous and potassium fertilizer. The nitrogen will enhance both top and root growth.

Overseeding an existing lawn is not the formidable task that a lot of people think it is. In fact it is almost like mowing the lawn two or three times in one day. Think spring in fall. Get next year's lawn started right now.

Paul Schnare of Cape Girardeau has been in the lawn and garden business for more than 20 years. He's an adjunct professor in horticulture at Southeast Missouri State University.