Help Columbia manage the threat of invasive Callery pear tree hybrids
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 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.)
- Alternative Trees
- Printable List of Alternative Treesopens PDF file
- About Callery Pear Trees
- About Invasive Callery Pear Hybrids
- How You Can Help
- About the “Stop the Spread!” Campaign
- “Stop the spread!” Brochureopens PDF file
- Alternative Tree Exhibit at Louisville Park
- City Channel Video: The Pear that Invaded Columbia
- “Pyrus, We Have a Problem: National Perspective on the Runaway Callery Pear”
New York State Urban Forestry Council – January 23, 2018
- “SMA Roundtable – Pyrus, We Have a Problem”opens PDF file
City Trees – July/August 2017
- “Stop the spread! Ornamental pears are invading!”
Missouri Conservationist – March 2011
- “KC WildLands works to combat attractive killers in prairies, woods”opens PDF file
Kansas City Star – May 3, 2010
- “Columbia, Missouri attempts to “Stop the spread!” of Callery Pear”opens PDF file
City Trees – Sept/Oct 2008 (Journal of the Society of Municipal Arborists)
- “Columbia Parks and Recreation fights back against invasive Callery pear trees”
Columbia Missourian – October 24, 2008
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.
|Printable list of Alternative Treesopens PDF file|
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.
- Ecological damage caused by displacing native plant communities
- Increased economic costs due to vegetation management problems near transportation corridors or under power line right-of-ways.
Potential threat to electrical and transportation services from falling branches or toppled trees because of these notoriously fast-growing, weak-wooded trees.
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.
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:
- 10,800 brochuresopens PDF file
- 1,500 postersopens PDF file
- Two newspaper adsopens IMAGE file
- Alternative tree exhibit with education signage at Louisville Park
- Information available on the Columbia Parks and Recreation web site
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:
- 5 – Red horsechestnut
- 7- Downy serviceberry
- 3 – American Hornbeam
- 5 – Redbud
- 5 – Yellowwood
- 3 – Dogwood
- 5 – Ironwood
- 3 – Blackgum
- 5 – Chokecherry
- 7 – Blackhaw viburnum