County Ag News

Callery pear–new invasive tree

 

Callery pear is a small ornamental flowering tree, which was originally brought to the U.S. from China in the late 1800s. There are currently a number of different cultivars sold as landscaping trees; Bradford pear, Chanticleer pear, Aristocrat pear, Cleveland Select pear. 

Callery pear is a fast growing tree used quite widely in landscaping that is tolerant of air pollution, has significant disease resistance, and has pretty white flowers in early spring. Bradford pear was the first popular cultivar and was widely used in landscaping from the 1950′s on. Cloning propagates cultivars, so that each individual is genetically identical. Because Callery pear is self-incompatible, Bradford pears could not pollinate themselves and produce fruits.  So on top of all the other advantages, it didn’t produce messy fruits.  

Unfortunately, Bradford pear had a big flaw–it has a weak branch structure, which resulted in the branches eventually splitting and killing the tree. To solve the splitting problem, horticulturists developed other cultivars with better branch structure. Over time, many other cultivars were released and used in landscaping. 

Each one of those cultivars is genetically different from the other cultivars, which means they can cross with each other and produce fruits, lots of fruits. Callery pear is also a popular root stock for grafting other pears.  If the grafted pear dies, the Callery pear root stock will continue to grow and will produce abundant fruits.  A single wild tree can spread quickly by seed and vegetative means, often forming dense thickets within several years and outcompeting native plants. In forested settings, it leafs out earlier than our native trees, effectively shading out spring wildflowers.

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