Apparently there are for more male trees planted than female trees, go figure.
"Male trees are one of the most significant reasons why allergies have gotten so bad for citydwellers in recent decades. They're indiscriminate, spewing their gametes in every direction. They can't help it—it's what evolution built them for. This is fine in the wild, where female trees trap pollen to fertilize their seeds. But urban forestry is dominated by male trees, so cities are coated in their pollen."
For the full article click here and don't forget to take care of those allergies.