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Callery Pear

Bradford Callery Pear (Pyrus calleryana ‘Bradford’): Is it really Sterile?

A native of Korea and China, this, now ubiquitous horticultural tree, was first grown from seeds by the USDA Plant Introduction Station in 1963. It is very easy to grow and transplant, has white flowers in spring, leafs out early, holds its leaves well into autumn and has good color in late November. It also resists disease and insects. No wonder it is grown and planted so widely. There is also a story, apparently believed by many landscape architects, that it does not produce viable fruit, in other words, that it is sterile. So no worries about it being invasive, right?

Well, unfortunately, it is not at all sterile. Most individual trees produce crops of small, brown fruit the seeds of which are quite viable. Evidence of this can be seen along Route 440 in south Staten Island in New York City in spring. Virtually all those trees with white flowers are Callery pears. It is also common on any abandoned field or lot in the New York to Phila. Corridor.

In fall, the fruit is noticeable as it drops on parked cars where pear trees line neighborhood streets. Starlings, robins, and other birds eat the fruit and deposit seeds with their droppings. Squirrels discard the fruit pulp under the trees and just eat the seeds.

So what is wrong with a few more Callery pears in natural areas? The problem is that they displace native trees like oaks and hickories that grow more slowly. As more land is covered with roads, houses, fill soils and commercial buildings, Callery pears and other exotic plants are escaping from cultivation and slowly crowding out native trees, herbs and grasses. This phenomenon is creating an “accidental,” man-made landscape that contains a few weedy, aggressive, fast-growing plants instead of a wide diversity of native plants that once grew in the region.

It is critical that all landscape plants be evaluated for their potential to escape and become “feral”. Just as no one wants rats, pigeons, starlings, feral cats or packs of wild dogs taking the place of native birds and animals, we must also protect our heritage of native plants against extinction by exotic, feral plants.


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