Successful seeding of cool-season grass coming out of winter

By John Torsiello

The success of cool-season grass seeding can be, if we use the current buzzword, problematic.

Thus, it is crucial to understand that cool-season turfgrass seed germination and establishment is highly sensitive to the cool soil and air temperatures that persist during late winter and early spring, making turf establishment during this period challenging, says Brad Park, sports turf education at research coordinator at the Center for Turfgrass Science at Rutgers University. “Among cool-season turfgrass species used for sports fields, Kentucky bluegrass is the most sensitive to cool soil/air temperatures, and perennial ryegrass is less sensitive.” He advised implementation of growth blankets that can be used to enhance seed germination and turf establishment through early spring.

Jeff Fowler, cooperative extension district director at Penn State University, believes one must select the proper varieties of grasses to get the best results for cool-season seeding. “Certainly, some varieties perform better than others. I recommend using the NTEP (National Turfgrass Evaluation Program) results when selecting varieties for use on athletic fields.”

Selecting a variety can be tricky. Knowing varieties that perform well in NTEP enhances the selection. He also sagely recommends not only looking at a state’s NTEP results, but also those of surrounding states and not limiting selection to a single characteristic. “Another great resource for variety selection is other sports turf managers. Contact other managers area to see if they have varieties that have worked well for them in their area.”

According to Mark Frever, director of grounds at Albion College, a blend of seed is better than selecting a single variety since each variety has strengths and weaknesses. For example one variety may have great drought resistance and one might have better insect resistance. This will provide a better chance of the lawn surviving different conditions. Also, a local turfgrass extension specialist or college representative can provide tremendous practical or research-based information to help a turf grower/manager be as successful as possible.

Timing of the seeding is also important, says Dr. Brian Horgan, extension turfgrass specialist at the University of Minnesota, “Often, soil moisture dictates the time in which we can get onto our fields to seed. Too wet and you will do more damage. If your fields tend to be wet in the spring, consider dormant seeding to have the seed in place when conditions are right for germination. Soil conditions and air temperatures drive much of your ability to be successful with early spring seedings.”

Frever opines that soil conditions can spell the difference between success and failure. “To understand your soil means to test your soil. Spend some extra money and work with a consultant to make corrections to the soil for optimum turf performance. Match your soil to the sport and never stop learning about soil.”

On sand-based fields, turf growers/managers have more control on when to seed, assuming there is an irrigation system to keep the seeds moist. Heavier textured soils can stay cooler longer or wetter longer. Use lightweight equipment to seed or dormant seeding may be a best option. In highly worn areas, seed often and don’t worry about the seeding rates. Says Dr. Horgan, “You are, in effect, managing an annual grass system, treat it like an annual and don’t worry about competition by plants. This is not to say that you should do this across the entire field, but identify those areas that should be treated differently and don’t be afraid to treat them differently.”

Although the time of year that the leaves fall has traditionally been considered the best time to seed for the following year, “we seed whenever conditions are favorable,” says Randy M. Haffling, general services manager at Moravian College, “We look at the long-range forecast to determine when to seed, so that temperature and moisture will ensure a successful establishment of new grass.”

Tongue placed firmly in cheek, Fowler recommends not planting during a “thunder and lightning storm or a tornado,” but other than that any day is a good day to put seed in the ground. “If you don’t have irrigation, time the seeding so that rain will speed up germination. Waiting until too late in the spring to plant without irrigation will put your success rate in jeopardy.” Early seeding gives the new seeds a chance to mature before they are played on. “If you are overseeding an already established field your reentry for play is sooner than when seeding an entire field. If you are seeding a new field make certain that you have enough time for the seed to mature before it receives play pressure.”

Brad Jakubowski, instructor of environmental sciences at Doane College, concurs that even though fall is considered the optimum time to establish grass by seed, spring can be a good opportunity to give fields a “kick-start” to the season. “Remember, if in doubt apply seed.”

Jakubowski advises studying the condition of the field; fill low spots, or make corrections to prescribed grades to ensure proper surface drainage and safe playing conditions before seeding. “As we know, seed-soil contact is paramount to getting grass growing efficiently. This can be accomplished in a variety of ways. Seeding in conjunction with aerification and verticutting are two of our best methods. Seeding in multiple layers or combining aerification and verticutting is also very good. Lately, we have been preseeding fields before aerification or verticutting.”

Park says never grade soil when wet, and that lime, organic matter, and nutrients should be incorporated via tillage prior to seeding. “Tilled soils should be firm at the surface but just loose enough to allow good seed-to-soil contact. When overseeding into existing turf (including very poor/thin turf cover) core cultivate and reincorporate cores to create a seedbed at the surface.”

Pamela Sherratt, sports turf specialist at Ohio State University, says slit seeding is ideal. “Disturbing soils in the spring by tilling creates a nightmare with weeds, so it should be avoided.”

A blanket recommendation is difficult for when to water. Too much or too little will delay or sometimes destroy a new seeding. Insure proper moisture by monitoring soil conditions. “Most people do not keep the seedbed wet enough during the first few weeks,” says Fowler. “If they can, I want the soil surface to be continually damp for the first 2 weeks. After that, reduce frequency of irrigation but increase intensity. Start off with a little often and end with lots infrequently. The trick it how you get from a to b.”

The first mowing of newly germinated seed should be done with care. Says Jakubowski, “The seedlings will be at a tender stage and severe scalping should be avoided. If the grass is to be maintained at 2 inches, let the grasses reach a 3-inch height, then mow.” If possible, avoid sharp turns on the newly grown grass and make sure the soil is not too moist, because wheel and foot traffic can create a compacted surface area. This can make it difficult for younger grasses to break through the surface. For shorter mowing heights, 1 inch for example, the first cutting could be at 2 inches then gradually reduced after each subsequent cutting.

Fowler believes that “under normal conditions” a new seeding should be mowed following the “one-third rule,” i.e., never remove more than one-third of the plant tissue in a single mowing. Allowing the new seedlings to grow to 3-4 inches before the first mowing won’t hurt as long as the rule is followed. Desired final height can be achieved after the plants have had some time to mature. “I find most people wait too long. I’d suggest mowing as soon as the leaf blades reach the mower, even if they aren’t removing much plant tissue. Mowing signals the plant to start tillering and the new seeding will fill in much quicker.”

Sherratt says to apply starter fertilizer with seed then again 3-4 weeks after, based on soil test results. “Only a couple of pre-emergents will be useful at time of seeding. Tenacity and siduron are both pretty good.” Post-emergent herbicides could be used after about the third mowing. If weed pressures aren’t too severe, holding off until the fifth or sixth mowing would help reduce any potential setbacks caused by herbicide applications.

Fertilizer should contain phosphorus to speed up the germination and establishment. A typical starter fertilizer with a 1-2-1 ratio is best at 1 pound phosphorus pentoxide per 1,000 square feet. Do not use a pre-emergent herbicide with the fertilizer, as doing so will impede germination of new seeds. Also, if weed pressure is a concern during grow-in, follow the herbicide label for proper timing.

Jakubowski says a starter fertilizer, such as a 12-25-10 with water soluble sources of nitrogen applied at 5-7 pounds of product per 1,000 square feet will be an effective nutrient source. “If a soil test revealed a deficiency in phosphorus, an application of a product like 18-46-0 would be useful. Subsequent fertilizer applications of water soluble sources of nitrogen applied at a rate of 0.25 to 0.5 pounds of nitrogen per 1,000 square feet every 2 weeks for the first couple of months would be recommended to ensure effective growth and fill-in. “Avoid using common pre-emergent herbicides like pendimethaline or prodiamine before the seeding process, as chemistries like these will prevent your grass seed as well as your target summer annuals. On areas with grass cover, the active ingredient siduron can be applied before seedling application. On bare ground, mesotrione can be applied before seeding as an effective tool to help prevent summer annuals as soils warm. Be sure to follow the labeled instructions for any of these herbicides during establishment.”

Park believes a complete starter fertilizer that contains nitrogen/phosphate/soluble potash (N-P2O5-K2O) starter fertilizer should be applied at the time of seeding. Following germination, use of phosphorous-containing fertilizers should be guided by soil testing; nitrogen becomes the most critical nutrient to encourage turf to fill-in and establish. “Mesotrione (Tenacity) and siduron (Tupersan) can be safely applied at the time of perennial ryegrass, tall fescue, and Kentucky bluegrass seeding to provide pre-emergence control of the weeds indicated on these products’ labels. Quinclorac (Drive XLR8) and fenoxaprop (Acclaim Extra) can provide postemergence control of grassy weeds; herbicide rates and timing are dependent upon the age and species of turf. Several mowings are typically required before traditional broadleaf herbicides (such as Trimec Classic and Confront) can be applied to newly seeded turf.”

John Torsiello is an independent writer/editor living in Torrington, CT and part-time in Mount Pleasant, SC. He has written on turfgrass maintenance issues for a number of years, and has won two First Place Awards from the Turf and Ornamental Communicators Association for pieces he authored.  

Tips for best seeding results

Brad Jakubowski’s (instructor of environmental sciences at Doane College) tips for seeding into soil and growing as quickly as possible:

  1. Mow the grass shorter than usual.
  2. Apply grass seed to the area at the recommended rate or slightly less.
  3. Aerify.
  4. Follow aerification with an application of grass seed.
  5. Aerify again.
  6. Follow aerification with another application of grass seed.
  7. Repeat steps 5 and 6 again if you prefer (like with shampoo: wash, rinse, repeat!)
  8. Topdress area with compost.
  9. Drag or work areas with rakes to distribute seed and compost.
  10. Apply starter fertilizer.
  11. Irrigate.

This process could easily include a verticutting step or steps intermixed with aerification. If possible, cover bare areas with a thin layer of mulch like pine needles (the acidity will not be a problem and will actually help) or straw to protect the new seedbed from wind, washing, or mowing. Hydromulching can also be an effective tool to ensure quicker germination. Diverting from the standard hydromulching process of mixing the grass seed in with the tank mix of water, mulch material, and fertilizer, I would recommend applying the grass seed to the field surface prior to the hydromulch application. Following the seed and hydromulch application, finish with a light rolling. This sequence aids in helping guarantee good seed-soil contact.

Priming or pregerminating (a process of soaking and draining seed prior to application) uncoated grass seed can also speed up the germination process and there are a number of ‘recipes’ available.