Plant growth regulators (PGRs) such as gibberellic acid (GA3), abscisic acid (ABA) and trinexapac-ethyl (TE) can be applied to turfgrasses to promote winter hardiness. Lethal temperature of 50% mortality measurements revealed that application of these PGRs had no effect on the acclimation status of creeping bentgrass and annual bluegrass for the months of January, February and March. Fall PGR application decreased acclimation status for annual bluegrass, whereas ABA and GA3 applications increased acclimation status for creeping bentgrass in April. Treatment with exogeneous ABA increased endogenous ABA levels in annual bluegrass. A simulated warming event in a growth chamber in late winter resulted in a loss of acclimation status for both grasses compared to a control. GA3 increased annual bluegrass photosynthesis and TE decreased creeping bentgrass photosynthesis during the warming event. PGRs are beneficial for maintaining the acclimation status of creeping bentgrass, while reducing the acclimation status of annual bluegrass.