By Sarah Browning, Extension Educator in Lancaster County
Traditionally, we think of seeding lawns in either spring (April–May) or fall (August–September). Of these two planting times, fall is the most successful. With a fall seeding, there’s less weed pressure than in spring, and late summer weather is less problematic (think rainy) during the soil preparation phase. Plus, the extended period of cool weather, usually with good rainfall, that occurs from September through late November is ideal for growth of cool season turfgrasses.
But increasingly, turf specialists are recommending a new option — dormant seeding. With this method, the area is prepared in fall but the seed is not distributed until after the growing season has ended. Seed remains in place, but does not begin to grow until soil temperatures are warm enough for germination in mid–April.
Dormant seeding has several benefits. First, soil preparation can be done at your leisure during dry fall conditions. There’s no rush to get the work done in a short window of time in spring between frozen soil and wet soil. Dormant seeded turf grows well and fills in during cool spring weather, preventing much of the potential invasion by weeds. Finally, plants have more time to develop vigor and hardiness before hot summer conditions arrive, making them more able to tolerate summer stresses.
SOIL PREPARATION CREATES A GOOD SEEDBED
The actual process of seedbed preparation is the same as other times of the year, but dormant seeding is most effective when soil preparation, such as core aeration, power–raking, tilling or some other form of cultivation is done in fall. Simply broadcasting seed and allowing it to work into the soil naturally through frost–heaving, might be effective; but having soil preparation done first to improve seed to soil contact, is important for successful dormant seeding.
Prepare small areas by hand raking to remove excess dead top growth and loosen the soil surface. Aeration is the best technique for preparing larger areas. It opens up the soil and provides a good surface for seed germination. Seeds that fall into the aeration holes will germinate and grow well; there is no need to topdress or fill in the holes before seeding.
Power raking can also be used to prepare the site, but is more damaging to existing turf. The only benefit to power raking over aeration is it can help reduce excess thatch if more than a 1/2–inch thatch layer is present. If power raking is used, go over the turf lightly only deep enough to penetrate the top 1/4–inch of soil.
SEEDING
Once seedbed preparation is done, dormant seeding can take place from mid–December through mid–February. Ideally soil temperatures should be 40°F or below to ensure seeds will not germinate. Since the seed needs to have good soil contact, don’t apply seed over snow. Dormant seeding should be done no later than March 15.
The seeding rate for new, bare lawn areas is as follows: Kentucky bluegrass 2–3 pounds per 1,000 square feet and tall fescue 6–8 pounds per 1,000 square feet.
The amount of seed applied when overseeding into a thin lawn is usually half the amount used for bare ground. Kentucky bluegrass should be applied at 1–2 pounds per 1,000 square feet and tall fescue at 3–4 pounds of seed per 1,000 square feet. When working with small amounts of seed, mix sawdust, dry sand, organic fertilizer or any other suitable material with the seed to aid in obtaining uniform coverage.
WEED CONTROL
Applying a pre–emergent herbicide for weed control can be done with new seedings, but use only the pre–emergent herbicides siduron, commonly sold as Tupersan, or mesotrione, sold as Tenacity. These herbicides will provide good control of annual grassy weeds like crabgrass and foxtail, yet still allow the grass seed to germinate.
Apply pre–emergent herbicide between mid–April and the first week of May. Several days of soil temperatures 55°F or above are required for crabgrass and foxtail seeds to germinate. Be sure the pre–emergent herbicide is in place before that time. Monitor your local soil temperature at Nebraska Extension’s Hort Update, http://hortupdate.unl.edu.
For new seedings, use the lower recommended rate and repeat the application one month later.
WATERING
Don’t rely solely on spring rain for germination of your new seeding. Begin watering the seeds 2–4 times per day in late April to ensure good germination. Base your watering schedule on weather conditions and how fast the soil dries. Water frequently enough to keep the top 1/2–1 inch of soil moist, but avoid over–watering and saturating the area.
WATCH WINTER WEATHER CONDITIONS
One risk involved with dormant seeding is warm winter and early spring temperatures. If conditions cause seed to germinate and are followed by a cold period, seedlings may be killed. Continuous snow cover provides the best protection for seeds.
Monitor seeded areas in mid–spring for the need to do additional overseeding, but give the seeds plenty of time to germinate.