Vaccinium macrocarpon Aiton (cranberry) exhibits phalanx and guerilla growth patterns. Phalanx modules (uprights) bear fruit, while guerilla modules (runners) are important in vegetative spread. Although cranberry is known to respond to edaphic variation through altered phenotypes (phenotypic plasticity), patterns in natural populations, especially southern marginal populations, are enigmatic. The objectives of this study were to characterize spatial clonal patterns and phenotypic plasticity patterns within two isolated V. macrocarpon populations in the Appalachian mountains. We used RAPD (random amplified polymorphic DNA) profiling to examine spatial clonal patterns and genetic heterogeneity. The Tennessee (TN) population was genetically homogeneous, as shown by nearly monomorphic RAPD profiles, where only five clones were detected. In contrast, there were over four times more clones discernible and higher molecular diversity in the West Virginia (WV) population. Clonal spatial patterns indicated that one clone was at least 350 years old. Nitrogen and phosphorus were manipulated at the two sites and reaction norms of predominant and infrequent clones within each population were compared to characterize plastic responses. Cranberries in TN were apparently more plastic than WV, although direct statistical comparisons could not be made. The TN population was plastic for more guerilla growth traits and the WV population for more phalanx traits in response to edaphic variation. Within WV, the predominant clone and infrequent clonal reaction norms of several traits to nutrients differed as revealed using a linear analysis of covariance/heterogeneous slopes model.