The callery pear, Pyrus calleryana, was introduced from China by the U.S. Department of Agriculture as an ornamental tree in the 1960s. The oldest cultivated variety, or cultivar, is the “Bradford” pear.
It tolerated all types of soils and had glossy green leaves and handsome white flowers each spring followed by small, hard, non-fertile fruits. It was a great landscape tree for 15 or 20 years until homeowners discovered that the trees’ weak branch structure did not withstand storms well, especially winter ice storms.
Going back to the drawing board, plant breeders created over 20 more genetically different cultivars, including “Aristocrat,” “Redspire” and “Cleveland Select,” also known as “Chanticleer.” The poor branch joints were remedied and those trees now offered lustrous, dark green leaves earlier in the spring, earlier and brighter autumn color, varied bloom times, resistance to fire blight disease, narrower profile, more compact size, and/or tiny, sterile fruits. Wow! What could be better? The potential for self-fruiting was minimal because cultivars were considered to be self-incompatible. That means genetically identical cultivars are unable to produce fertile fruit.
However, by the late 1990s some communities contained large numbers of ornamental pear trees of many cultivars. One cultivated variety of ornamental pear could have been planted along the community’s downtown streets. Homeowners who admired these good-looking trees could have planted other varieties of callery pears in their home lawns.
If these different cultivars were close enough for cross-pollination during bloom, then fertile fruits formed. Birds, especially European starlings, ate the softened fruits in late winter and dispersed the seeds to nearby fields, rights-of-way, parks and other sunny open areas. Thickets of callery pears appeared. Spring brought prolific white flowers and autumn provided an attractive display of red leaves in undeveloped areas.
The problem is that those thickets of trees bearing abundant and early leaves crowded and shaded out native plants, reducing ecological diversity. The introduced species have few natural enemies, including insects, so this non-native forest does a poor job of feeding native birds, especially nestlings. There is also the cost of vegetation management, compounded by the thorniness to which these plants have reverted.
What should we do? Avoid planting callery pears is the short answer. Some cities have banned planting additional callery pears. A few states have prohibited the sale of callery pears.
What should we do with existing plantings? Prune off sprouts from the base of callery pear trees. Often, the shoots are from grafted rootstock and their flowers can cross-pollinate with the cultivar above. It is not feasible to replace existing street and landscape plantings immediately, but as these trees decline or become damaged, they should be promptly removed.
What should replace them? Always select non-invasive species. When possible, use native trees, such as serviceberry, also called shadbush and Juneberry, Amelanchier species; eastern redbud, Cercis canadensis; flowering dogwood, Cornus florida; yellowwood, Cladrastis lutea; white fringetree, Chionanthus virginicus; hophornbeam or ironwood, Ostrya virginiana; American hornbeam, Carpinus caroliniana; or varieties of red maple, Acer rubrum.
Remember that not all non-native species are invasive and many make good choices as replacements for callery pears. The Japanese tree lilac, Syringa reticulata, is similarly shaped and does well in this area. There are narrow varieties of flowering crabapples with gorgeous spring flowers that are followed by tiny, persistent fruits that do not make a mess. With a little research, you will find many choices for your landscape instead of callery pears.