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By Steve Roark

Columnist

 

You have undoubtedly noticed all the white flowering trees that have been put on a show for the past couple of weeks along roadsides, fence rows and field edges.

They are Bradford pears, a popular landscape tree, noted for their beautiful flower blitz, symmetrical round crowns, and supposedly sterile so as not to produce messy fruit to clean up. That last part was a total failure, and the tree has gone Frankenstein and spread rapidly to become an exotic invasive plant, a threat to our native plants and even our farmlands. This wasn’t supposed to happen, so what the heck?

Bradford pear is a cultivar of Callery pear, a native to China. When a breeding program finally produced a tree with the above-mentioned desirable qualities, the Bradford hybrid was grafted onto pear rootstock in vast numbers to supply the huge demand for the tree.

So initially, almost all Bradford pear nursery trees are clones and genetically identical (referred to as genotype) and were found to be self-incompatible, meaning they cannot fertilize themselves to produce viable seed. 

But life on our planet wants to make babies, and so nature found a way. Bradford pear limbs are weak due to a branch structure that produces narrow crotches, allowing limbs to shear off easily along the wood grain when heavy snow or wind events occur. A solution was sought, and cultivars were bred using an Asian pear (a different genotype) that produced a more robust limb structure.

So when this variety was planted into landscapes, it could cross pollinate with Bradford and both could produce heavy crops of fruit, which look like small, speckled berries that contain viable seeds. Another way cross-pollination can occur is graft jumping. As mentioned, Bradfords were produced by grafting cuttings onto the seed-grown rootstock of another pear variety. Rootstock is commonly used to sprout and grow branches that can produce flowers. When that happens, the tree will have flowers from two different genotypes and can thus cross-pollinate and produce fruit with seeds.

Birds come along and consume the fruit, then fly off and poop out the seeds for miles around, so trees are now growing where they don’t belong. They are strong competitors with native plants and can become a nuisance. They grow a massive root system that is hard to kill out. They can produce thickets that are very hard to remove once established. Some wild trees have genetically reverted back to ancient Chinese Callery pears that can have long, sharp thorns that are nasty to mess with. There are a few insect or disease problems that need to be kept in check by the Bradford population.  

There is some thought that the tree is allelopathic, meaning it can produce chemicals in the soil that prevent other plant seeds from germinating.   

Bradford appears poised for world domination. I jest a little, but the reality is that, from my observations, wild Bradford pears have at least tripled in population in the last two years. So maybe you like the angelic appearance of this pear all over our landscape, but please believe me, they are devilish in the trouble they cause. So if you own land, even just a fence row, eradicate this enemy with extreme prejudice wherever found. 

Steve Roark is a volunteer at Cumberland Gap National Historical Park.