Comment by OutOfHere
7 hours ago
Doesn't pollen also have to do with the "gender" of the trees? In gendered trees, male trees emit pollen and female trees intercept pollen. Not all species of trees are gendered (dioecious) but various are. If reforestation uses male trees at the expense of female, then pollen count will be higher.
Urban developers who make the mistake of using male trees, because they don't drop fruit/berries/seed pods, will make the residents suffer pollen. Sugi and hinoki apparently are not gendered -- they're monoecious.
Most trees (about 75%) contain both male & female flowers. Of the rest, about half are species with separate male/female trees and about half have separate male/female flowers (on the same tree).