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 Invasive Pear Hybrids at Forum Nature Area |
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The abundance of ornamental pear trees being planted within our community is of critical concern. There has been a recent phenomenon of ornamental pear cultivars crossing and creating an invasive wild population of hybrid Callery pear trees.
These hybrid pear trees hold the potential to create a substantially negative economic and ecological impact on our community forest. There is already evidence that the spread of invasive pears is gaining a foothold in our community and parks. (See photo of local example above.)
Columbia Parks and Recreation, in cooperation with the Missouri Department of Conservation, launched a "Stop the spread!" campaign. The focus is to encourage the community to stop planting Callery pear trees in order to protect and improve Columbia's urban forest.
The following examples of native trees make desirable alternatives to Callery pear cultivars. These species possess one or more of the following attributes: beautiful fall foliage, ornamental flowers and/or fruit. Talk to your local nursery to learn more about the various seasonal attributes of these lovely native tree species.
 Dogwood
(Cornus Florida) |
 Redbud (Cercis Canadensis) |
 Yellowwood (Cladrastis Lutea) |
 Blackhaw Viburnum (Viburnum Prunifolium) |
 Hophornbeam (Ostrya Virginiana) |
 Downy Serviceberry (Amelanchier Arborea) |
 Chokecherry (Prunus Virginia) |
 Blackgum (Nyssa Sylvatica) |
 Red Horsechestnut
(Aesculus Pavia) |
 American Hornbeam
(Carpinus Caroliniana) |
Bradford pear (Pyrus calleryanna 'Bradford') and other similar Callery pear cultivars could be called the "universal landscape tree." They have been a frequently planted tree species of many community urban forests throughout the United States and Missouri since the Bradford pear was first developed and introduced by the USDA in Glenn Dale, Maryland in 1960.
Recognized for their ornamental appeal, the popularity of these Callery pear cultivars has grown rapidly due to their attractive appearance, ease of care and availability. There are now nearly 26 genetically differing Callery pear cultivars, including such well known selections as Aristocrat, Bradford, Redspire and Chanticleer. These were once considered appealing landscape trees, but due to their cross-breeding, they are now identified as a problem plant pest.
In the past, the potential for self-fruiting had generally been minimal because cultivars of Pyrus calleryanna were considered to be self-incompatible, unable to self-pollinate or produce fertile fruit from a genetically identical cultivar.
However, by the late 1990's, it had become apparent in communities with large numbers of ornamental pear trees that many cultivars had unexpectedly begun to interbreed fairly readily. The hybrid fruit is eaten by starlings and other birds. The seeds are then dispersed into nearby fields, right-of-ways, parks or other natural open areas. Highly variable, many of the seedlings show characteristics such as thorniness that had been purposely bred out of their parent cultivar.
Hybrid Callery pear seedlings in a fallow field adjacent to
Scott Boulevard in Columbia, Missouri
The Callery pear progeny are now aggressively invading fields and other open areas, much like other introduced exotic plant species, such as Amur honeysuckle. The following consequences can occur as a result of this interbreeding:
It would not be feasible to immediately replace all of the pear trees that currently exist in our community. Instead, as these trees deteriorate or become unhealthy, they should be promptly removed to eliminate a source of pollen and seed.
The solution to this invasive issue ultimately lies in the hands of homeowners, landscapers and developers. Please consider one of the many non-invasive alternatives to Callery pear trees when undertaking new landscape projects or large community developments. A decrease in the number of Callery pear cultivars and hybrids would be beneficial for our entire community to potentially reduce power outages, save costs of trimming and tree removal, and create a more ecologically balanced community forest. Educational brochures and posters for the "Stop the spread" campaign are available at the Parks Management Center, 1507 Bus. Loop 70W, Columbia, Missouri. Contact 573-874-7201 to make arrangements to pick up a poster. |
 Fruit of Pyrus Calleryanna Each fruit can hold up to ten seeds |
The "Stop the spread!" campaign is a multi-faceted approach to managing invasive Callery pears in our community, which includes an educational program and clearing and removal work. The budget for the project was $15,664, with the Missouri Department of Conservation contributing up to $9,896 through their Tree Resource Improvement and Maintenance (T.R.I.M.) Grant and the City of Columbia providing a match of $5,768 in force account labor, equipment costs, and donated labor from the TreeKeepers.
The following were included in the educational component:
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A tree exhibit was created at Louisville Park to showcase native trees that homeowners and developers can choose as alternatives to Callery pear trees. An educational sign is posted at the tree exhibit and the following 48 trees were planted in 2008 by Parks and Recreation staff and TreeKeeper volunteers in the demonstration area:
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 Educational Sign at Louisville Park Tree Exhibit Click on image for enlargement |
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