Thursday, March 24, 2011

Bradford Pears Go Bad

Bradford Pear - Wikimedia
Bradford Pear trees are in bloom - everywhere!  The beautiful blossoms seem to have captured the hearts of home owners both urban and rural.  Driving down the four mile stretch of rural Highway W southeast of Ozark, Barb stopped counting after the the first 200.

Their spring blossoms make them an appealing tree to line a long rural drive to the house or surround your pond.  Unfortunately, they are as appalling as they are appealing.  If you look around neglected fields and unused commercial sites, you will start to see them scattered, sometimes 10 or 12 over an area, other times in clusters like a shrub.  They are the latest invasive tree species that we are aware of having created.

The Callery Pear (Pyrus calleryana) is a species of pear native to China.  They were developed to meet an aesthetic need of home owners.  The initial variety produced sterile fruit and therefore could not reproduce.   The most frequently planted were the Bradford variety.   Their dense upward growth, so desirable in urban plantings, is because of the narrow weak crotches of their branches.  This leads to their short life spans and excessive damage from wind and ice storms.

New cultivars were developed to produce stronger trees but crossbreeding has produced seeds which are fertile.  Wikipedia reports that the species has escaped and naturalized in 152 counties and in 25 states in the United States.  They are officially declared an invasive species in Pennsylvania, Delaware, Maryland and Illinois.  An MDC article explains how this happened.
"There are two causes. One is due to the fact that ornamental pears have been over planted 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 cross-pollinate 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 the flowers of the tree itself.  These small fruits are eaten by birds and are then scattered along fences and roadways, pastures, abandoned fields, natural areas and under power lines.  Wild trees then sprout from these fruits and begin reproducing quite quickly. In fact, wild callery pear trees start producing flowers and spreading themselves after just three years. 
Some of the characteristics of wild callery pears are similar to the callery pears they originate from.  They grow quickly, flower prolifically and will tolerate a wide variety of soils, character traits typical of an invasive weed.  Moreover, some of the new wild trees are bringing back characteristics of the original trees from China like very large, stout thorns, making a field filled with wild callery pears difficult to clear."
 What should we do about Bradford Pears?  The MDC article has complete suggestions for managing existing Bradford Pears as well as alternatives to plant when your trees decline.  Another comprehensive resource is the Columbia Missouri "Stop the Spread" website which shows pictures of 10 varieties of flowering native trees.

You may want to forget about this when you are out driving in the country or around Springfield.  Otherwise you too may start driving passengers nuts by counting trees like Barb.

2012 update at

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