Bob Mugaas, University of Minnesota Extension Educator
Photo 1 (above): Thin lawn area that could benefit from dormant seeding. Bob Mugaas.
One last shot at lawn improvement can be done even yet this fall. By early November, most lawn care chores and activities are completed; lawn mowers are put away, watering has ended, hoses are drained and stored for the winter, irrigation systems have been blown out and winterized and, the last, late season nitrogen fertilizer has been put down. Yet, there remains one activity that can still be done to help repair or thicken the lawn for next year. In fact, prior to the early part of November (at least in the Twin Cities area, earlier in the northern half of Minnesota), it would be have been too early to do this task. That task is known as dormant seeding. It is best employed when wanting to reseed bare soil areas or help thicken up thin lawns. It is not as effective, where lawns are thick and dense with little opportunity to achieve the good seed to soil contact necessary for the grass seeds to germinate and grow next spring.
The Dormant Seeding Process
Dormant seeding involves putting down seed while the ground is
not frozen, yet cold enough so germination of the grass seed will not
occur until next spring when the soils begin to warm. In fact, seeds
that do germinate late in the season often do not survive the winter
because the very young, immature seedlings have a difficult time
surviving those harsh conditions. Other than the time of year of dormant seeding, the
actual process of preparing the area to be seeded is virtually
identical to establishing grass from seed at other times of the year.
Choosing Well Adapted Seed
When choosing the seed to use, be sure to select seed mixes that are well adapted to both your site conditions and the amount of maintenance you expect to provide during the growing season. For average lawn conditions, mixes containing some Kentucky bluegrass, fine fescue and small amounts of perennial ryegrass can be sown about three to four pounds per 1000 ft2.
Photo 2 (left and above): Vertical rotating tines of a vertical mower, sometimes termed a power rake. Bob Mugaas.
Establishing Good Seed to Soil Contact
Success of any grass seeding process depends largely on good seed to soil contact. Therefore, the initial step in preparing the area is to loosen the soil surface so the seed can easily be incorporated into the surface half-inch or so of loose soil. Small areas of bare soil or even a thin turfgrass stand can easily be prepared using a hand rake. Larger areas of sparse turfgrass can be prepared by 'lightly' going over the surface with a power rake or vertical mower available from most rental agencies. Set the blades just deep enough to penetrate into the top ¼ inch or so of soil. This will also help remove small thatch layers that may be present, as well as any dead grass plant parts laying on the surface of the soil.
Rake up the grass plant debris that was brought to the surface from this process so that it will not interfere with sowing the grass seed. This debris can easily be composted or used as a mulch in another area of the landscape. Remember these units are NOT intended to be used as rototillers. They are designed and used to remove thatch with only light penetration into the surface soil. Hence, use them appropriately; your rental service will appreciate your proper use of their equipment.
Photo 3 (left): Using a vertical mower to prepare lawn/soil surface prior to seeding. Bob Mugaas.
Another machine known as a slit seeder could also be used. This machine creates a shallow slit in the soil into which the seed is dropped, lightly covered and packed down. There are some rental businesses that have such a unit available. More commonly this is a practice hired done by a lawn care professional.
Watering Thoroughly, but Not Too Much
Once the seeds have been properly sown and lightly incorporated into the existing soil, water the area thoroughly and leave until next spring. By this time of year, our cool to cold temperatures and short days will help keep the areas moist far longer than in summer. While just barely damp soil is okay, it is important that the area does not become soggy and saturated with water. If the weather does turn a little warmer and drier and the area starts to dry out, it may be necessary to lightly water the area just to keep it damp and prevent it from becoming too dry. However, in most cases it will be unnecessary to do this.
What to Expect for Next Spring
Above are the essentials for the process known as dormant seeding. The degree of success from your dormant seeding efforts will depend on the overwintering conditions afforded to the newly seeded areas. In most cases, the seed is best protected when we receive snowfall(s) that will cover and protect those areas during fluctuating weather conditions often experienced during a Minnesota winter. Even with good preparation, it may still be necessary to do some overseeding in the spring in those areas where little grass emerges. If the newly seeded areas appear to be a little thin, you shouldn't necessarily feel your fall efforts were a failure, as it is quite common to have to do a little additional reseeding in the spring. However, do allow enough time for the seeds to come up the following spring. Don't be too hasty to get in and start tearing things up; you just may be destroying all of the good work done the previous fall.
For those of you who postponed doing some lawn seeding earlier last summer, consider doing some dormant seeding yet this fall. It may be just the ticket to give you and your lawn a jump start next spring.