Methods: Tape lifts were collected from low-lying leaves of trees and plants (<6 ft. height) in the yard of a single family dwelling in London, Ontario. The top and bottom leaf surfaces were both sampled for pollen on random days between June and August 2015. Counts from the NAB London station and occurrences of rain were examined for correlations.
Results: Findings indicate that tree pollen was sequestered among other plants long after (>1 month) pollination had finished. Significant amounts of pine and oak tree pollens were unscavenged by rain, hidden on the underside of leaves, even as pollen counts for London were virtually zero. Huge amounts of pollen from ferns were found on low-lying leaves, but not among the diaspora captured by the NAB station, whereas the amount of grass and weed pollen on leaves tracked with the NAB London counts
Conclusions: Protracted exposures may be significant for allergy sufferers who react even when pollen levels are reportedly low. This work of aerobiology reflects the meanderings of wayward pollen, once freed to take flight, only to seek respite. The findings show 1) unsuspected reservoirs of pollen close to home may explain persistence of allergies. 2) Ferns are among the choice of decorative garden plants; their allergenicity has been noted elsewhere. Their contribution to prolonged suffering may go unnoticed as stations ie. NAB, Pollen.com, etc. do not report fern pollen.