Rhododendron is known from seeds in the Paleocene of England. All other reports, including those from North America, are based on fossil leaves, many of poor quality. In addition, the foliar characters of fossil Rhododendron may mimic those of the leaves of several genera of Fagaceae, requiring great care in identification. Thus, pre-existing reports of Tertiary age North American Rhododendron require verification. We report seeds clearly assignable to Rhododendron from the La Porte Flora of Northern California. This flora has been dated by whole rock 238U/205Pb methods at 33.2 Ma (corrected), placing it in the Early Oligocene, but the climatic affinities of the flora suggest that it is pre-deterioration and thus likely of Late Eocene age. Thus, Rhododendron had achieved at least a Euramerican distribution by the Eocene. Rhododendron seeds fall into three morphological categories which bear some association with the higher order systematic divisions of the genus. Our investigation suggests that the variability of seed morphology is such that identification to lower taxonomic groupings is not possible.

Key words: California, Eocene, Ericaceae, fossil, Rhododendron, seed