It happens every spring. Unsuspecting city walkers find themselves on streets lined with Callery pear trees exploding with clouds of delicate white flowers when suddenly, an odd and malodorous smell hits them. With top notes of chlorine and undertones of dirty sock, the blossoms of the lovely-to-look-at Callery pear tree have the sad misfortune of harboring the funkiest of scents.

As a New York Times editor, Juliet Lapidos, puts it in The Awl, “You can tell it’s spring if it smells like semen.”

The Callery pear, known to tree people as Pyrus calleryana, is a deciduous tree commonly planted in cities and towns throughout North America, much because it is fast growing and tolerant of pollution and other extreme conditions such as de-icing salt and compaction. It provides lovely color in the fall and nice shade in the summer, preceded by a beautiful spring display and off-putting reek that has earned it an entry in the Urban Dictionary under “Semen Tree.”

The 2006 New York City Parks Department tree census listed 63,600 Callery pears in the city, making it the third most common city tree after the London planetree and the Norway maple.

Which means that for a few weeks every spring, the city has 63,600 trees spewing the scent of semen, yet for New Yorkers, it barely seems to register. Aside from some online commentary about the topic, including the above mentioned story and a funny post in The Frisky, it seems that perhaps we New Yorkers are so commonly deluged by the smells of the city that we just don’t pay the pear trees much mind.

But for those who do — those of us, for example, who may need to tightly close our windows against gentle spring breezes reminiscent of ammonia-tinged Brie — there may be some bittersweet relief.

As Lapidos reports in The Awl, the Callery pear is prone to splitting as it ages, and since they’re borderline invasive, they’re falling out of favor with urban parks departments. New York currently plants only a mere 20 or 30 Callery trees a year, while thousands are lost to age and storm damage. Jeremy Barrick, deputy chief of forestry, horticulture and natural resources at the Parks Department, predicts that by the 2015 tree census, the Callery will have dropped to a meager 30,000 or so, a swift decline for a tree of such beauty.

To be sure, its easiness on the eye will be truly missed, but its assault to the nose, not so much.

Related story on MNN: It's not the only tree that smells ... funky

City 'semen trees' on the wane
The future isn't looking great for the Callery pear, an urban tree beloved for its beauty but bemoaned for its odor.