Populations of Magnolia macrophylla Michx. in Gaston County, North Carolina, and one in neighboring York County, South Carolina, were examined using allozyme analysis. All populations studied had the same monomorphic genotype. Several factors could account for this lack of variation. Migration from population centers along the Gulf Coast by sequential founder events could have resulted in populations at the northeastern limit of its range being genetically depauperate. Sexual reproduction in these populations is rare because most trees do not appear to live long enough to reach maturity. Recruitment of new individuals seems to be by vegetative reproduction of ramets from roots of immature trees. Any pollen exchange that does occur is between trees that represent another part of a single clone.