Red spruce (Picea rubens Sarg.) suffers frequent and extensive injury to current-year foliage during the winter. Experimental freezing of red spruce foliage at cooling rates > 10 degrees C min(-1) induced visible symptomatology similar to natural winter injury at the branch, needle and cellular levels. Such damage was associated with a low-temperature exotherm near -10 to -12 degrees C, a loss in needle fluorescence, massive cellular disruption, foliar discoloration, and low needle survival. Susceptibility of individual trees to rapid freezing injury was associated with historical winter injury patterns and alterations in foliar nutrition. We conclude that anthropogenic deposition may alter the sensitivity of trees to winter injury caused by rapid temperature changes.