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The Coming Plague of Pears

While driving the Capital Beltway around  Washington, D.C. this past April I began noticing a large number of white flowering trees in the areas just off the road.  For the following three weeks I continued to see these same white flowered trees everywhere.  They weren't dogwoods.  They weren't wild cherries or shadblow Amelanchier.  Finally, driving along Route 450 in Bowie, my curiosity got the better of me and I pulled off the road and had a closer look at one of these trees.  It was a pear.  Not the common edible pear, Pyrus communis but the ornamental pear, Pyrus calleryana.  It was obvious from where these trees were growing they weren't planned plantings.  These trees were coming up wild and in tremendous numbers.  In the spot in Bowie, I counted over one hundred trees in a stretch of neglected ground about 100 feet long and 50 feet wide.  They were so thick that in places the individual young trees grew only a foot or two apart.  We seem to have a new horticultural plague on our hands in Maryland, a plague of pears.

In 1918, the USDA was searching in China for improved root-stock plants for our commercial pear varieties.  More than 100 pounds of Pyrus calleryana seed was brought back and sown at the USDA Plant Introduction Station in Glenn Dale, Maryland. A vigorous non-spiny seedling, found among the normally spiny Pyrus calleryana seedlings was selected out and given the name Bradford.  The Bradford pear was quite a tree.  It was fast growing, had dark shiny leaves and had a wonderfully formal shape.  It grew easily and was adaptable to a wide range of site conditions. It wasn't troubled by bug or disease, and it was loved universally by the nursery world, landscaper, and homeowner. In 1982, the National Landscape Association voted it the second most popular tree in America, just behind the flowering crabapple.  Oh yes, there was another nice thing about the Bradford pear, since most trees were identical clones, propagated by grafting, it didn't self-pollinate and didn't produce fruit.

The Cinderella story of the Bradford pear ended once it was discovered that these trees begin to fall apart when they reach an age of about twenty years, right at the pinnacle of their landscape glory.  The very narrow crotch angles of the erect and plentiful branches are weak, and a gusty thunderstorm or a coating of wet snow or ice will bring the branches crashing down.  In an attempt to make a better Bradford there appeared a succession of new callery pear cultivars.  These had improved, or at least different, branching patterns with less chance of the branch breaking problem.  Now the Bradford was not alone.  There were other callery pears in the landscape to keep it company.  There was the Aristocrat pear, and the Chanticleer pear, and the Redspire pear.  There was also something else.....cross pollination among the callery pears.  Suddenly Bradford and the other pears began to produce fruit.  True, the fruit was small, an inch or less in diameter, but some of the trees produced very large quantities of this small fruit.  In some way, and I suspect it may be the birds, the seeds within the fruit is being disseminated far and wide and new hybrid callery pears are popping up in every vacant lot and along every roadside throughout the area. 

Whether or not a plethora of wild, ornamental pears is a plague depends on who eventually cleans up the ground on which they are rising up like new sown grass.  Mowing over an overgrown patch of weeds is one thing; removing hundreds of four and five inch caliper trees is quite another.  I live down the road apiece in Southern Maryland, and the other day I was picking up trash along the county road right-of-way in front of our house.  Standing straight and tall out of the long grass and ragweed plants were two broom-stick stem-sized callery pear seedlings.  The invasion is on.