What's that awful smell? Cat urine? Semen? Rancid butter? Possibly one of these gorgeous city trees?

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Sources:
http://www.slate.com/articles/health_and_science/science/2016/10/why_we_still_plant_smelly_ginkgo_trees.html
http://arnoldia.arboretum.harvard.edu/pdf/articles/2008-66-2-wake-up-and-smell-the-ginkgos.pdf
https://motherboard.vice.com/en_us/article/qk97b3/trees-smell-like-vomit-jizz-barf-semen-spring
https://www.pubs.ext.vt.edu/3010/3010-1464/3010-1464.html
http://www.dcnr.state.pa.us/cs/groups/public/documents/document/dcnr_010311.pdf
http://extension.psu.edu/natural-resources/forests/private/tools-resources/publications/invasive-plants-and-insects/tree-of-heaven
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Images:
https://en.wikipedia.org/wiki/File:Ginkgo_Biloba_Leaves_-_Black_Background.jpg
https://en.wikipedia.org/wiki/File:GinkgoLeaves.jpg
https://en.wikipedia.org/wiki/File:Ginkgo_biloba_MacAbee_BC.jpg
https://en.wikipedia.org/wiki/File:Ginkgo-biloba-male.JPG
https://en.wikipedia.org/wiki/File:GingkoFruitingTwigSpring.jpg
https://commons.wikimedia.org/wiki/File:Gingko_fg01.jpg#/media/File:Gingko_fg01.jpg
https://en.wikipedia.org/wiki/File:Pyrus_calleryana.JPG#/media/File:Pyrus_calleryana.JPG
https://en.wikipedia.org/wiki/Ailanthus_altissima#/media/File:G%C3%B6tterbaum_(Ailanthus_altissima).jpg