Q & A WITH PAMELA SHERRATT

With a mixed ryegrass / Kentucky bluegrass field , is it possible to shift back to a majority KBG surface through overseeding ; or is it better to go all-in on ryegrass to have a more uniform surface ? – Dan , New Jersey

The short answer is yes , it is possible to shift back to a majority Kentucky bluegrass field if you are overseeding bare soil / thin areas with 100 % bluegrass seed and you have prepared a good seed bed with a slit-seeder , weasel or similar . Overseeding a dense perennial ryegrass sward , and hoping that bluegrass will establish is futile .

Regularly overseeding thin and bare soil during optimum bluegrass germination and establishment times is key . The ideal time to seed is fall — from mid-August to late September — due to cooling temperatures , timely rains , no competition from crabgrass or goosegrass and seven to eight months of root development and maturation before the summer stress period . Bluegrass does not do well mid-summer when average daily temperatures are above 75 degrees Fahrenheit , especially if it ’ s dry .

The challenge in spring will be weed control because bluegrass is just too slow to out-complete aggressive spring weeds such as annual bluegrass , prostrate knotweed , crabgrass , goosegrass and yellow nutsedge . Avoid renovations during peak crabgrass germination period and consider applying an herbicide such as mesotrione that will control weeds but not have an adverse effect on bluegrass germination . Dormant seeding in late winter is also an option to get a jumpstart on the season . Pre-germinating the seed and mixing it with divot mix is also a good tip , as the divot mix can be applied to highwear areas and bare spots after each game .

The main reason bluegrass overseeding fails is lack of moisture . The seed needs to be kept moist until it germinates . This means that someone must commit to lightly watering ( syringing ) the seed several times per day for one to two weeks until the seedlings are visible . Even then , there must be a robust fertilizer , irrigation and mowing program to get a dense , healthy ground cover . In essence , it ’ s a high-maintenance grass and the reason that many sports field managers use perennial ryegrass .

In response to your question about going all-in with perennial ryegrass , many cool-season turf managers do overseed with just ryegrass , but you must be vigilant for disease . Three of the grass-killing diseases — brown patch , pythium and grey leaf spot — can kill ryegrass quickly . In some cases , the inoculation period is so quick that by the time you see the disease , it is too late to save the grass . Protecting the ryegrass with a preventative fungicide program can prevent major grass loss , but it can be expensive . There are more disease-tolerant cultivars available , but keep in mind that new , seedling ryegrass is more susceptible than established ryegrass , and that while some cultivars are more tolerant , no cultivar is immune .

Having a mixed sward of the two species provides the best of both worlds . The perennial ryegrass will give you quick ground cover , great color and striping ability , and a hard-wearing surface . The bluegrass will give you great color and striping ability , a hard-wearing surface that can recuperate via rhizomes and pretty good disease tolerance ( bar summer patch ). If the crown stays hydrated , bluegrass can survive several weeks of drought stress and be able to recuperate ; perennial ryegrass typically cannot . To further maximize sward diversity , several cultivars of each species can be added to the mix . Most managers rely on their seed supplier to make sure the mix is uniform in growth habit , color , cultural requirements and mowing height .

Further complicating the issue of uniformity , certain cultivars of Kentucky bluegrass will react differently if you are on a plant growth regulator program . Some bluegrass cultivars will become very compact and dense when under regulation , while others will not . I recommend putting out a test plot so you can evaluate how your field will respond to certain growth regulators and other products . SFM

Pamela Sherratt Sports turf extension specialist The Ohio State University

Questions ? Send them to Pamela Sherratt at 202D Kottman Hall , 2001 Coffey Road , Columbus , OH 43210 or sherratt . 1 @ osu . edu

Or send your question to Dr . Grady Miller , North Carolina State University , Box 7620 , Raleigh , NC 27695-7620 , or grady _ miller @ ncsu . edu

50 SportsField Management | August 2023 sportsfieldmanagementonline . com