Juniperus ashei

Juniperus ashei (mountain cedar or Ashe juniper) pollen is one of the most potent airborne allergens in North America. Male J. ashei trees produce abundant pollen that is easily dispersed by wind. In addition to being very allergenic, mountain cedar pollen is also unique due to the time of its pollen release. Pollination occurs during December and January often with the peak occurring in mid-January. The pollen is responsible for a winter hay fever problem that is called "cedar fever" in Texas.

Populations of this species are found in the Arbuckle Mountains of south central Oklahoma and in the Ozark Mountains or northern Arkansas and southwestern Missouri, but the largest populations occur in central Texas on the Edward Plateau. Although no populations occur within 200 miles of Tulsa, we have presented evidence for the long distance transport of J. ashei pollen being carried to Tulsa and beyond by prevailing southerly winds. In most years mountain cedar is captured in Tulsa samplers on 40% to 50% of the days in December and January, and very high concentrations of this pollen have been frequently recorded.