An article was posted this week on NPR blaming seasonal allergies on botanical sexism, a term coined by Tom Ogren, horticulturalist and author. He attributes ‘exacerbated allergies’ to America’s love for male trees. To review some basic botany, flowers have male parts—stamens (an anther and a filament) and female parts—pistils (stigma and style). Whether a plant has flowers that contain only one sex or both sexes is another story, and plants exist across an entire range of possibilities. Some plants have perfect flowers: flowers with both male and female plants; some plants have imperfect flowers: only male or only female flowers. The male parts of the flower, the anthers, produce pollen. The female parts, the stigma, receives the pollen which travels down the pollen tube in the style and fertilizes the egg to create a fruit with seeds. Some plants are monoecious and will have all perfect flowers or imperfect flowers of both sexes. Some plants strictly have imperfect flowers and are dioecious and thus there will be separate male and female plants.
The article claims that urban forestry is biased towards dioecious male trees. Without female flowers, there will never be any fruits—But why are fruits undesirable? Think of the ginkgo tree, which lines NYC streets and has stinky fruits that make a mess when they fall off the tree into the streets below. Female Ginkgo trees are even banned from being planted in Durham, NC. It’s an interesting theory, that cleaning up pollen was thought to be an easier and a fix-all for messy fruits. On the flip-side, if all female plants had been planted instead, there would be no fruits OR pollen. Female flowers can’t set fruits without pollen.
The article left me wondering if botanical sexism and the preference of male dioecious trees really is what’s going on, or if the straight up lack of diversity in trees used in landscaping is more at the root of it. I can’t say for every city, but take a drive around Miami and you’ll see landscaped areas with the same plants over and over. For lots of reasons (and not just to curb your allergies) it’s important to plant a diverse group of native plants. Native plants exist naturally in an area. In contrast to exotic plants are introduced, like the ginkgo, which is only found in the wild in China. Native plants are typically very low maintenance, adapted to local environments requiring less water. They don’t require copious amounts of fertilizers and pesticides. They also attract local birds, butterflies, and other wildlife. If you’re interested in discovering native plants in your area, the National Audubon Society has a database, searchable by zip code.
Though having trees is better than no trees, it’s important to understand that trees, and plants in general, have a myriad of differences. Not only in the interest of allergies or diversity, awareness of the variety of our natural world is important for a healthier planet.