Abstract
To forecast the release of white birch (Betula platyphylla var Japonica) pollen release without any tools, we studied the daily growth of male flowers, sprouts, and female flowers from September to the end of May when all male flowers had fallen. We also observed daily pollen counts and patient numbers reporting their first nasal allergy attack. Six days after male flowers began to droop, 5 days after all dangled, pollen release began as their color changed from black to rust. Seven days after sprouts with a pair of leaves became claw-shaped, 5 days after leaves assumed a V shape, and 2 day after a line from the top to the base across the other top of the pair of leaves became straight, release began. Once leaves had bent backward, release had already begun. When female flowers pointed upward, release began. These findings forecast the first day of pollen release.
