It all boils down to a concept called “botanical sexism” which was first termed by horticultural epidemiologist Thomas Leo Ogren.
Ogren has been studying the allergy-potential of common horticultural plants for 30 years and has even written several books on gardening techniques for mitigating allergies.
Botanical sexism involves the process by which urban landscapers, in an effort to keep city streets and sidewalks clear of seeds and flowers, plant only male trees.
The male trees lack the seeds of their female counterparts but have an abundance of pollen, and as the trees get bigger, their pollen counts increase.
In an article for the Scientific American, Ogren discusses the timeline of male trees dominating city streets.
In an effort to replace them, many landscapers opted to plant clonal male trees.
“The problem is that while these trees and plants are “litter-free,” they all produce abundant allergenic pollen,” Ogren told Scientific American. »
