They describe the process like this: "During the late summer and early fall, the plants must prepare themselves for winter through a process called cold acclimation. This process is initiated by the cooler temperatures and shorter daylengths that naturally occur at this time of the year."
Proper care includes providing nutrients (through fertilizers) during active growth in warmer seasons, withholding excess nitrogen fertilizer in fall. Westerfield and Lindstrom explain:
"Fertilizing plants in the fall (after August or September) with a fertilizer high in nitrogen can cause a flush of new growth that is more susceptible to cold temperatures."