Springtime blossoms on trees and flowers are a wonderful sight to behold in south-central Indiana, at least most of the time.
One of the earliest flowering tree species is the Callery pear. People may know the trees as Bradford or Aristocrat pears, which are cultivars of the Callery pear. Although the pear trees are beautiful, they have become one of the fastest growing invasive plant species in the area.
Originally, the pear trees were brought into the United States from China because they are resistant to fire blight, which was killing U.S. pear trees. They were first introduced to the country in the early 1900s. Most of the trees were used as root stock, with other pear tree varieties grafted in to produce pears. Since the Callery pear tree doesn't really produce quality pears itself, it wasn't until the 1950s that it became a popular ornamental tree.
"It doesn't produce edible fruit," said Ellen Jacquart, director of northern Indiana stewardship for the Nature Conservancy and a member of the Monroe County's Identify and Reduce Invasive Species (MC-IRIS) group, about Bradford pear trees. "They can't produce fruit; they're a perfect yard tree."
But that perfect yard tree has problems. First, the tree's branches are prone to split as it ages. Add in Midwestern thunderstorms and wind events like the one the Bloomington area experienced recently, and you get a lot of trees that are splitting and branches crashing to the ground.
Other cultivars of the Callery pear are less prone to splitting branches and have other desired traits. Those varieties, including Autumn Blaze, have been introduced to the U.S. and are often planted near the Bradford varieties. That allows the pear trees to cross-pollinate, producing fruit. The fruit on those trees ripens in late summer and fall and then turns into little brown balls hanging on the tree.
After the first frost, that fruit "turns to goo and falls off the tree," Jacquart said. "The sidewalk is then just slimy with this goo."
Besides creating brown goo, the fruit is often food for birds. It's a particular favorite of starlings, Jacquart said. The birds then spread the seeds throughout the area.
"We have watched thousands of Callery pears grow up along State Route 37," Jacquart said. "You will see hundreds, hundreds of these along the roadways."
The Callery pear varieties often grow very close to each other. In areas where the trees have spread, the pear trees are crowding out the native flower and tree species that normally grow there. Right now, the pear trees are covered with white blossoms, making them easy to see. It's the time Jacquart and other members of MC-IRIS are busy mapping those locations. The hope is members of MC-IRIS and other volunteers can eventually help remove the trees.
Anyone with a smartphone who wants to help map where the pear trees are growing along roadsides can use the app Report IN that can be found at eddmaps.org/Indiana. Even people who don't have smartphones can use Report IN to add their information to the database.
"It's so simple to do," Jacquart said of Report IN. "In less than 60 seconds, you can report an invasive species."
Jacquart and other members of MC-IRIS also want people to realize they should not be planting ornamental pear trees anymore. The hope is that people will instead plant native trees.
"A lot of the trees that Bloomington planted in the past were Callery pears, and that's unfortunate," Jacquart said. "We, the Midwest Invasive Plant Network, did a video on pear trees — what you shouldn't plant in your yard. The tree was Callery pear."
Jacquart said the plant network traveled to Martin County, just south of Bedford, to video the pear trees because Martin County has one of the worst infestations of ornamental pear trees in the nation. "This video shows just how bad it is there," she said.