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Autumn is the best time to seed and repair your lawn

Contrary to popular thought, spring is not the best time to start new lawn or patch bare spots in our lawns. Spring is actually the second best time to plant grass seed. In Minnesota, planting some time between mid-August and mid-September gives you the best chance of success.

Why is August or early September a better time to plant grass seed? First of all, weather is usually cooperative. Warm daytime temperatures encourage rapid sprouting and at the same time, nights grow longer and cooler. This means there will be plenty of time for good roots to develop before hard frosts and as we move into September, the likelihood of rainfall increases.

Weeds are one of the worst problems when you plant grass seeds. Many weed seeds lie dormant in the soil for years, just waiting for the right conditions to germinate. The tender care you give to newly seeded areas provides just the right conditions for those weed seeds to germinate and they will compete for moisture and nutrients.

Fortunately, most weed seeds are programmed to sprout early in the season. Therefore, if you seed in autumn, grassy weeds like crabgrass and foxtail, as well as broadleaf weeds will not compete with the grass seedlings and they will have a greater opportunity to become established before winter.

Perennial weeds, like quackgrass, tall fescue and ground ivy, are a different story. Not only do they sprout from seeds like annual weeds, they grow back every year from roots and rhizomes that have survived over winter. Since there are no selective grass weed killers and broad leaf herbicides will damage or destroy young grass, it is necessary to rid the area of perennial weeds before you plant.

If you are overseeding a thin lawn, spot spray with a non-selective herbicide such as glyphosate (Roundup and others) a week or ten days before seeding. If you are starting a new lawn or completely renovating an existing lawn, it will probably be necessary to spray the entire area before seeding the new grass.

One of the greatest causes of failure when overseeding existing lawns is lack of good seed to soil contact. Seed simply cannot germinate and grow if it is not in contact with receptive soil. Rake out the dead grass and debris in the area to be overseeded and then rough up the soil using a steel garden rake.

After preparing the soil, sprinkle some seed over the area and then cover it lightly by pulling a flexible tine leaf rake in one direction across the seeded area. Use fresh seed and seed with bluegrass and fine fescue mixtures at the rate of 3 to 4 ounces per 50 square feet or if pure Kentucky bluegrass seed is used, seed it at the rate of 2 to 3 ounces per 50 square feet.

Though excessive amounts of fertilizer can burn grass, it is necessary to incorporate a starter type fertilizer into the soil when you plant grass seeds. You need not wait until the grass is up and established. In fact, the best opportunity to work phosphorus and potassium into the root zone is before planting since these two nutrients don't move much in most soils.

Remember that although we have legislation prohibiting the use of phosphorus containing fertilizers on our lawns, starter fertilizers containing phosphorus can be used when seeding a new lawn. This would be a good time to have your soil tested to learn exactly which nutrients you need to add for good grass growth. Do not use any weed and feed products in areas where you plan to seed or on young grass plants until the following spring.

Contrary to popular belief, you do not need to keep grass seeds constantly wet. For best germination, be sure that there is moist soil to a depth of 4 to 6 inches before seeding. After seeding keep the surface soil moist by watering lightly a couple of times a day and then as seeds germinate and begin to grow, gradually shift to deeper but less frequent watering.

Keep the newly seeded areas moist until you are ready to mow for the first time, and then gradually increase the interval between waterings until the soil dries slightly before you water again. Overwatered, saturated soil not only leads to root rot and other lawn problems, but also wastes water.

Don't be afraid to mow young grass. When newly planted grass reaches a height of three and a half to four inches, cut it back an inch. It is important that your lawnmower blade is always sharp when mowing grass, but even more important when the grass is young.

Gradually reduce the mowing height as temperatures cool, but never cut the grass shorter than two and a half to three inches. If you are overseeding into an existing lawn, keep the existing grasses mowed fairly short until the newly seeded grasses have had a chance to germinate and catch-up with the other grasses.

For more information, contact me at the Polk County Extension office in McIntosh or at the Clearwater County Extension office on Wednesdays. Our toll free number is 800-450-2465, but if e-mail is your thing, contact me at

Source: Carl Hoffman, Stearns County Extension Service