Annual bluegrass comprises a large portion of putting green turf in the Northeast.  Failed attempts to control this weed have led to its adoption as part of the playing surface and cultural practices have been adapted to improve putting conditions in a mixed creeping bentgrass and annual bluegrass turf.  One such practice is the use of plant growth regulators such as mefluidide and ethephon for suppressing annual bluegrass seedheads in spring.  The two most common programs include application of mefluidide plus foliar iron or ethephon plus trinexapac ethyl when growing degree days at base 50 (GDD₅₀) reach 50 units.  These programs are notoriously inconsistent for annual bluegrass seedhead suppression.  Suppression varies each year and ranges from 20% to 95% for ethephon and 40% to 95% for mefluidide.  Attempts to reduce application frequency or increase the number of spring applications have led to turfgrass injury.  Close observation of annual bluegrass on golf putting greens in early spring will show that many plants have already initiated seedhead production before 50 GDD₅₀.  Some plants have been observed to produce an occasional seedhead under snow.  We hypothesized that inconsistency in seedhead suppression over years is largely due to variable amounts of annual bluegrass plants that initiate seedhead production during winter, driven primarily by periodic warm winter temperatures or thermal heating under snow.  Our objective was to determine if applications made in late winter could improve annual bluegrass seedhead suppression from standard ethephon or mefluidide programs compared to these programs without the early treatment.  We also included demethylation inhibiting fungicides (DMI) in some treatments to determine if several combined components of the program might accumulate and lead to turfgrass injury if mixed with use of a plant growth regulating fungicide.  Two field trials were conducted on putting greens mown at 3 mm.  One trial was in Blacksburg, VA and the other was in Harrisonburg, VA.  Treatments were arranged in a randomized complete block design with three replications.  The "early" application was applied on March 4 and the putting green was still brown from winter stress.  The normal program application dates were April 15 applied at 48 GDD₅₀ and four weeks later.  On April 28, annual bluegrass seedhead coverage was 47% in the nontreated check and equivalent in the ethephon early treatment, ethephon normal program, and with a single treatment of triadimefon.  When the ethephon early treatment was combined with the normal program, however, seedhead coverage was reduced to 0 to 7%.  The early treatment of mefluidide reduced seedhead coverage to 20% and all normal programs of mefluidide either alone, with the early treatment, or with the early treatment and triadimefon completely eliminated seedhead production.  Similar trends occurred on May13^th; however, on May 26^th, all normal program treatments regardless of early treatment or DMI fungicide completely controlled annual bluegrass seedheads, presumably because the second normal program treatment had been applied prior to this rating.  Early treatments and/or triadimefon did not increase turfgrass injury compared to normal mefluidide or ethephon programs alone; however, the normal program of mefluidide injured turf 30 to 60% and significantly decreased normalized difference vegetative index (NDVI) from April 15 to May 13 while ethephon did not cause injury or decrease NDVI.  These data suggest an early application of seedhead inhibitors can improve annual bluegrass seedhead suppression when applied prior to a normal GDD₅₀-timed program, especially in the case of ethephon.