Stop the Spread!

How’s this for a creepy sci-fi movie? Humans transport aliens to Earth without worry because we are sure they cannot reproduce here. Thirty years later a quiet, spectacled scientist discovers that the aliens are spreading. Indeed, alien offspring multiply and escape to our farms and parks, crowding our youngsters that are desperately trying to hang on… you get the point.

Now, replace the word alien with ornamental pears and you’ll see this is not sci-fi but a real-life dilemma. Ornamental pears are spreading in Missouri and causing quite a stir with landowners.

Ornamental pears were introduced to the United States in the early 1960s and came from China. All ornamental pears originate from Pyrus calleryana, or callery pear, commonly referred to as Bradford Pear. Bradford is indeed the oldest cultivar, or kind, of ornamental pear. Newer cultivars include Chanticleer, Aristocrat and Cleveland Select, to name a few. Ornamental pears were originally very popular trees due to their prolific spring flowers, dark glossy leaves and ability to thrive in almost any kind of soil—and because people thought they were sterile and therefore had no messy fruits to contend with.

The first major downfall of ornamental pears came 15–20 years after the initial trees were planted. At that point, many unsuspecting homeowners found out that the branches and trunks of pears split in storms. Many reading this article can relate to waking up after a windy night to their prized yard tree ripped down the middle and lying across their driveway. Also, ornamental pears are more susceptible to a fungal disease called fire blight than was hoped when they were first introduced.

However, it has not been until the last few years that people have been noticing the ornamental pears we thought could not spread … are. And, they are doing so quite prolifically. In fact, 26 states have reported wild callery pears spreading in the past decade. How could this have happened?

There are two causes. One is due to the fact that ornamental pears have been overplanted in our communities. Although each different kind of callery pear cannot reproduce by itself, it turns out that when these many types of pear are all planted close together (like they are in our towns) they can crosspollinate and produce fruits. The other method of ornamental pears reproducing is if the sprouts that sometimes grow from the base of pears are not pruned they can flower and crossbreed with