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Science and the Environment

Bradford Pear Trees: An Invasive Species

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David Stonner
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Bradford pear trees are one of the first tree species to bloom in the spring and feature delicate white flowers.  Their nice, manicured shape makes them desirable landscape trees.  But, while they may seem innocent, they have a dark side.

Paul Johnson, forester with the Missouri Department of Conservation, said the Bradford pear is one of many cultivar species of the Callery pear, which was brought to the U.S. from China and Taiwan almost 100 years ago.

"It was originally brought to the United States to be used in agriculture.  The species itself, Callery pear, shows some resistance to fire blight, which is very common in the Midwest," Johnson said, "and so the idea was they could cross-pollinate and develop a fruiting pear that we have that is resistant to fire blight.

According to the Missouri Department of Conservation, “the cultivar 'Bradford' was named for Frederick Charles Bradford, one of the chiefs at a USDA plant station in Maryland in the early 1950s, who noticed the tree's ornamental qualities and began work to develop the cultivar named for him. 'Bradford' pear was released to the public in 1963, 12 years after Bradford's death.”

While the Bradford pear is sterile against itself, Johnson said when it’s planted in close proximity to other Callery pear species as well as native pears, it can cross pollinate and produce thousands of viable seeds.  That’s a problem, according to Johnson.

"Because it's able to naturalize by cross-pollinating, the birds are spreading it very well, other wildlife species are spreading it very well, and so it's quickly taking over fields," Johnson said, "and it can also take over some woodland-type settings underneath shady canopies, but where it's been most successful is old fields, old lots, things like that."

Johnson said Callery pears will shade out native vegetation, especially early spring wildflowers, and as they grow bigger they choke out native trees.

They can also have thorns.  According to the Department of Conservation, after a fallen tree is removed, sprouts appear at the stump and will grow into the wild, thorny, invasive form of the tree, whose fertile fruits are spread by birds and other animals.

"So, they're kind of becoming kind of a nasty little tree," Johnson said.

They’re most prolific near urban settings and have increasingly become more of a problem in the last 20 years, according to Johnson.

While Bradford pears have some desirable characteristics, including their nice shape and white flowers (despite their not-so-pretty smell), the trees have a difficult time staying upright.

"Windstorms and everything like that can affect them.  They're short-lived species," Johnson said.  "They also do pretty well in about any soil type, and that's why they've been widely planted everywhere.  But the big problem is, because they're not very hardy, they break easy, and they are very good at naturalizing and taking over our native landscape."

Johnson advises people not to plant Bradford pears.  Instead, he encourages them to plant flowering native species.

"The hawthorns, any hawthorn variety, has a nice, white flower, the serviceberry, it's an early spring flowering tree, that's a nice one, and there's several varieties--cultivars--that you can purchase.  You can also go with flowering dogwood, American plum or eastern redbud, and, of course, redbud is going to be a pink flower," he said.

For help dealing with a large Callery pear infestation on your property, Johnson suggests contacting your local Missouri Department of Conservation office and asking for the private lands conservationist or forester.