We often praise trees as the green lungs of our cities—but some may be quietly making us sick. For decades, urban planners have favored male trees over female ones to avoid the 'mess' of fruit and seeds. The unintended result is a pollen overload that worsens allergies and asthma for millions. This overlooked form of botanical bias is now being reexamined as cities grapple with rising health complaints and environmental inequality.
As allergy seasons worsen, it might be time to ask: are our city trees part of the problem, and can smarter planting make us breathe easier? Click on to find out.