Cities throughout the U.S. and beyond have been making a consistent effort to line sidewalks, medians, and other vacant areas with trees. This brings shade and sustainability to otherwise pollution-dominated places. Let’s have a closer look at the decision making behind these developments:

Transparency

After researching this topic in cities around the east coast, I can confirm that most of them are extremely excited to share the work their government has put in planting trees in urban spots. Cities like Philadelphia and Washington D.C. even have interactive maps that sport specific tree species and location. Other cities, such as Baltimore, have comprehensive public lists of every type of tree they plant. This is very exciting for those of us with sustainable mindsets who are interested in learning more. However, this doesn’t mean only good news.

What Trees Are Allowed?

When given the information that many cities provide on this topic, it’s only natural to look into what trees they gravitate toward planting for the public. A lot of the choices made have to do with the puzzle of urban infrastructure. The city of Baltimore has two separate lists for the trees they plant and maintain: some that can be planted around or under power lines, and others that can only be planted in open air space.

One overwhelming agreement found between many city and state tree lists is that they all prefer ‘male’ trees. In fact, many trees listed that have certain differences between male and female variants are specified with a “male only” in parenthesis. To know why that is, let’s first make a list of these differences.

Monoecious Trees:

• In a plant or invertebrate animal, monoecious simply means that the organism possesses both male and female sex organs, or both pistillate and staminate flowers.
• For trees, this means having both male and female flowers or cones, essentially self-providing the means for reproduction.
• Monoecious fruit trees are often banned in cities for their potential for reproduction and debris.

Dioecious Male Trees:

• Dioecious organisms require two opposites to come together, each providing half of the means of reproduction.
• In trees, specifically the male variety, this means growing flowers or cones which produce pollen with a mission: to pollinate seeds of female trees.
• Pollen produced by male trees is a large contributor to seasonal allergies.
• Male trees have been proven to grow faster and live longer than their female counterparts

Dioecious Female Trees:

• While male trees produce pollen, female trees produce fruit, pods, or seeds.
• Some interesting dioecious fruits include asparagus, pistachio, persimmon, kiwi, spinach, hemp, mistletoe, yam, papaya, mulberry, and plenty more.

So, Why Only Male?

To start, cities like to keep their tree population under control and forbid free growth. When both male and female trees are within the same proximity, they can pollinate and reproduce. For sustainability, this is a good thing. For city planning, not so much. My question is, what are we clinging to? Modern day city life is, in many ways, destroying the earth as we know it.

Male trees produce pollen, which, when unchecked by female trees, will gather in the air and intensify seasonal allergies. The “good” side of this dilemma is that males cannot produce fruit, seeds, or pods, which equals less maintenance and cleanup for the city to fund. It also conveniently means that the homeless population won’t be able to “steal” fruit from public trees. All of us will have to make money in order to purchase this wonder of nature from the grocery store.

Final Takeaways

Although there are certainly many ways to interpret the information presented here, I think we can all agree that our local governments have some explaining to do about the truth behind some of the sustainable action plans that they back. If we are not maximizing the potential for sustainability and equity in our society, then what are we doing?

References

DC Street Trees Map. (n.d.). Casey Trees. https://caseytrees.org/resources-list/d-c-street-trees-map/

Farr, M. (2022, September 13). Cities are planting trees. Why not make them fruit trees? Grist. https://grist.org/food/cities-planting-fruit-trees-food-justice/

NYC Street Tree Map. (n.d.). NYC Parks. https://tree-map.nycgovparks.org/

Street Trees Species List for Baltimore. (2015, December 23). Department of Recreation & Parks. https://bcrp.baltimorecity.gov/forestry/treebaltimore/species-list

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