(a post from my intended occasional series about invasive plants, plants I don’t recommend, and things I see flowering along Route 422)
Every year around now people ask me what those beautiful white flowering trees they see along the highway are. The answer: they are the callery pear (Pyrus calleryana). To answer the followup question: no they are not native, and yes, they are an invasive species.
The callery pear is a popular landscape tree which is still favored by landscape designers for their nice floral display, nice fall color, and toughness (the brand-new Wegman’s in Pheonixville has them in the parking lot). They’ve fallen out of favor in Philly as a street tree, because the most popular cultivar (‘boulevard’) has a habit of shedding very large branches on parked cars, powerlines, and (oh yes) houses. If I were king, planting these things would be banned, but I’m not, so go ahead and plant them if you really want to (but honestly, folks, the pear trees that make pears for eating are just as pretty, not invasive, and give you tasty fruits).
The other followup question is “are they really pears?”, and yes, they are. By late summer a careful observer will see that they’re covered in blueberry-sized, yellowish-green fruits, which hang on the tree after the leaves drop in the fall. They’re not poisonous, but having tried them I can say they’re pretty bland, and very seedy. Someone who’s not me might try making jam out of them some winter (people who make jam get bored in the winter, after all).
Just to re-iterate (send me some hate mail, grammarians!), this is an invasive species. The national park service (which does its best to take care of Valley Forge, as you may know) doesn’t like them one bit. They’re said to spread via birds that eat the fruit and poop out the seeds, but I suspect they also spread via deer poop (I know for sure that goats love the fruits, so presumably deer like them too), and via wind along roads (the little fruits bounce quite well).