The northern range of eastern mistletoe, Phoradendron serotinum (Viscaceae), and its status in Ohio. 1

SPOONER, D. M. (Dept. Botany, The Ohio State Univ., Columbus, OH 43210). The northern range of eastern mistletoe, Phoradendron serotinum (Viscaceae) and its status in Ohio. Bull. Torrey Bot. Club 110: 489-493. 1983.The northern limits of Phoradendron serotinum (Raf.) M. C. Johnston have often been believed to have been determined by cold temperatures. A map of the northern range of the species, from Long Island to Missouri, was constructed from herbarium specimens and published data. The northern limit is correlated with the mean minimum January temperature of -4.5°C. Areas where the gross climatological data do not fit the distribution of the species are in areas where mistletoe grows in locally warmer areas that are not reflected in these data. Field work in Ohio, part of the northern range of the species, has demonstrated that the majority of the present-day distribution is along the Ohio River from Washington County downstream, in areas that are kept relatively mild by the moderating effect of the river. The most northern inland Ohio populations, previously documented, are now believed extirpated. A disjunct Cuyahoga County record mentioned by Trelease (1916) is possibly in error. The Ohio populations have undergone reduction in recent years due to over-collecting, cutting of host trees, and the severe winters of 1977-1978.