Public agencies typically specify male tree species when possible for most tree planting on public property. This practice helps reduce maintenance tasks because male tree species do not produce seeds that can create litter and potential slipping hazards. This “botanical sexism” has the unintended consequence of increasing pollen levels in neighborhoods where these male trees grow, which impacts those with allergies, asthma and other respiratory diseases. Female trees produce seed, but do not produce pollen.
The Benicia Tree Foundation uses the male species for Gingko biloba (Maidenhair Tree). A male Gingko does not produce fruit which people find foul smelling.
Pistacia chinensis or Chinese Pistache is another tree that grows well in Benicia, but the female species produces seed clusters that can cause slipping hazards on sloped pavement. In that situation we have planted the cultivar ‘Keith Davey” which does not produce seed clusters or pollen. Cultivars are plant species that have been bred by humans to produce certain traits.