Today, all types of allergies affect over 30% of adults and 40% of kids in the US. According to a study in 2012, pollen levels are expected to double by 2040. Pollen-producing male trees – they’re all around us. Many parks and backyards are surrounded by pollen-laden male-only trees based on the recommendation of a 1949 USDA report that they should be planted instead of female trees, which give off no pollen. but more female trees can make a better outside for all.