Leaf samples were collected at four times during the 1974 growing season from black cherry trees growing on the Allegheny Plateau of Pennsylvania. Foliar concentrations of N, P, K, and Mg were dependent on sampling date. Variability of foliar Ca was such that no sampling date difference could be detected. N, P, and K levels declined during the growing season. Late August appears to be the best time to collect leaf samples from black cherry trees growing in the region. FOREST SCI. 23:429-432.