3 years agoJune 6, 2010
In our urban landscapes we now have the most manipulated kind of city forest ever seen. In the past twenty years landscapers have grown inordinately fond of using male trees. In dioecious species (separate-sexed) there are separate male trees and separate female ones. Female trees and shrubs do not produce any pollen, ever, but they do produce messy seeds, fruits, old flowers, and seedpods. Landscapers and city arborists consider this female byproduct to be “litter”, and they don’t like to see it lying on our sidewalks.
As a result we now have huge tracts of these litter-free or ‘seedless’ landscapes in our cities. What these actually are, of course, are male clones. As males their job is to produce pollen, and that they do! Even though in many cities we have less total vegetation than we used to, we have more pollen in our air now than ever before.