We are now well out of the window for successful seeding this fall, but dormant seeing is the next best timing after late summer seeding for establishing cool-season grasses. Following is a summary of points to maximize success of dormant seeding.
Timing: Any time after soil temperatures are about 40F in order to guarantee no germination until next spring. Seeding between Thanksgiving and St. Patricks’ Day is a good rule of thumb.
Soil preparation: Though simply broadcasting the seed and allowing it to work into the soil naturally through frost-heaving can be effective, it is better to improve seed-soil contact with aerification, power-raking, tilling, power-overseeding, or some other form of cultivation. Wet or frozen soils will likely determine which cultivation is best for each situation, but maximizing seed-soil contact is essential for successful dormant-seeding.
Species: Kentucky bluegrass or tall fescue work best, but avoid perennial ryegrass since it may germinate in a mid-winter warm-up only to die in ensuing cold temperatures. We are pretty sure buffalograss can also be dormant-seeded, but early research shows it might not be as effective as with cool-season grasses.
Seed rate: Our current recommendation is to seed at 10-25% higher rates than normal to account for seed loss via erosion, animal feeding, etc. Seed Kentucky bluegrass at 3.0 lbs/1000 sq ft, tall fescue at 10 lbs/1000 sq ft, and buffalograss at 3.5 lbs/1000 sq ft on bare soils. These rates can be cut by as much as one half if overseeding into existing stands with thin turf. Our current research is reevaluating the seed rates for dormant seeded turf and we’ll know more by next summer.
Mulch on bare soils: Mulch is likely not required, but may reduce potential erosion or seed movement. A tackifier will be required on the mulch to minimize wind loss during the winter. Hydroseeding can be used on bare soil if air temperatures are warm enough. Erosion blankets or sod should be used on highly erodible areas.
Fertilizer: Starter fertilizer should be applied next spring as the seedlings emerge. Apply 1.0 to 1.50 lbs P2O5/1000 sq ft depending on soil test levels. This same fertilizer and same rate should be applied again four to five weeks after emergence and maybe again at eight to ten weeks after emergence depending on the density of the new stand.
Irrigation: Dormant-seeded areas will need irrigation just like any new seeding. Irrigate as often as needed to maintain moisture in the top ¼” of soil, which may mean irrigating once or twice per day. Irrigate less regularly and in larger volumes as the seedlings establish. However, dormant-seeded areas may need irrigation all summer as these relatively young plants will not be mature enough to withstand drought stress.
Mowing: Early mowing on any newly-seeded area encourages lateral spread and quick fill-in. On most areas, set the mower 10-20% lower than the regular mowing height for the first 3 to 5 mowings to encourage the most rapid fill-in. Mow as soon as the first few leaves of the seedlings reach the mowing height and mow regularly thereafter (in spite of only apparently affecting a small percentage of the plants) to maximize fill-in.
Weed control: Dormant-seedings will be emerging early next spring so most PRE herbicides cannot be used over dormant seeded areas. However, early weed control is critical to minimize weed competition and maximize establishment. In some cases where weed pressure is high, it is justified to apply herbicides early at the risk of turf damage. Even if damage occurs, the remaining turf will likely recover and thrive in the absence of competition. Regardless of the product selected, be sure to refer to the label for specifics. Once the seedlings are mature enough, PRE herbicides including dithiopyr, prodiamine, or pendimethalin can be applied, and this will likely be at the approximate timing of the second application in typical sequential applications of PRE herbicides (mid-June).
Mesotrione (Tenacity) or siduron (Tupersan) can be used in the seed bed and will likely provide three to four weeks of PRE control of crabgrass and other weeds. Tenacity is especially effective as a PRE on bare soils but much less effective as a PRE on turfed soils.
SquareOne (quinclorac+carfentrazone) can be applied within 7 DAE of tall fescue or Kentucky bluegrass for POST control of crabgrass and broadleaf weeds.
Mesotrione (Tenacity) can be applied POST to Kentucky bluegrass or tall fescue at 28 days after emergence (DAE) to control crabgrass and some broadleaf weeds.
Dithiopyr (Dimension, Dithiopyr) can be applied once the root system is well established and after at least two mowings for PRE/POST control of crabgrass.
Quinclorac (DRIVE XLR8, Quinstar, Quinclorac, and others) can be applied PRE or 28 DAE of Kentucky bluegrass and anytime over tall fescue for POST control of crabgrass and some broadleaf weeds
Carfentrazone (QuickSilver) can be applied at any time after seeding for POST broadleaf weed control
Stay tuned for more information on seeding and you will hear much more about seeding at the Nebraska Turf Conference in Lavista on Jan. 7-9. Registration and information will be available at online at www.nebraskaturfgrass.com shortly.
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Zac Reicher, Professor, Turfgrass Science, zreicher2@unl.edu