Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Ah, spring. The sun is out, the streets are humming, the days are getting longer, and the air smells like… like… um… say, can anyone else smell that? It’s not just me, right? Right?? It’s not just me. All over America, spring is getting smellier every year, and the culprit is the Bradford pear, a tree that gained popularity in the mid-20 th century for its ornamental properties. But it has since proven to be kind of a nightmare. As well as its distinctive smell (described as smelling like rotting fish, sweat, or semen), it has a nasty habit of shedding branches during storms. Its hardiness makes it awfully difficult to get rid of, to the extent that it’s now considered invasive in most of North America. Oh, and you can’t eat its fruit, either, because it’s full of cyanide. The tree isn’t just a problem here in the US, either.…