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Species
Pyrus calleryana Dcne.
IUCN
NCBI
EOL Text
United States
Rounded National Status Rank: NNA - Not Applicable
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Pyrus+calleryana |
The Callery Pear (Pyrus calleryana) is native to eastern Asia but planted widely as an ornamental in urban and suburban residential and commercial areas in the United States. Numerous cultivars have been developed and are clonally propagated. Wild populations of Callery Pear can now be found throughout much of the United States, generally in open or disturbed habitats.
The Callery Pear was originally brought to the United States to address the problem of fire blight, a bacterial disease spread by pollinators, that was affecting Common Pears (Pyrus communis). In the early 1900s, the cultivated pear industry in the western United States was suffering enormous losses due to fire blight. Callery Pears were used in breeding programs and as rootstocks in efforts to develop resistant cultivars. The ornamental value of the Callery Pear was soon recognized and by the early 1960s the "Bradford" cultivar was commercially available. The Bradford Pear quickly caught on and became a widely planted street tree. Many other cultivars followed--and it was realized that Bradfords had a problem in that the architecture of the branches often caused individual trees to split under their own weight after around 15 to 20 years of growth. The shortcomings of the Bradford Pear increased the popularity of other varieties and the diversity of Callery Pears being planted.
In recent years, Callery Pear trees have begun to appear in many natural areas in the eastern United States. By 2005, wild trees had been found in more than two dozen states. Interestingly, the Callery Pear was not long ago viewed as unlikely to become an invasive species in part because of its self-incompatibility. Like many plants, Callery Pear exhibits a gametophytic incompatibility whereby when pollen is transferred pollen tubes begin to grow down the styles of both compatible and incompatible flowers, but if the haploid pollen grain shares the same self-incompatibility allele as the diploid maternal tissue, the pollen tube is prevented from reaching the ovule. It is now apparent, however, that as a consequence of the increasing diversity of the cultivars being planted, and the sprouting and flowering of rootstocks that are from different genetic stock than the scion, this incompatibility is often circumvented. Numerous other traits (e.g., seed dispersal by birds, broad environmental tolerance, few pests. rapid growth, early reproduction, and heavy fruit set) facilitate the rapid spread of the Callery Pear. Naturalized Callery Pears often form dense thickets and these are often thorny since even thornless cultivars apparently retain genes for thorniness that may be expressed in their mixed ancestry progeny. Although there is significant concern about the ecological impact of the Callery Pear in the United States, it remains to be seen whether it will ultimately persist as a minor non-native component of the ecosystem or will become a more serious problem,
(Vincent 2005; Culley and Hardiman 2007 and references therein; Hardiman and Culley 2010)
License | http://creativecommons.org/licenses/by/3.0/ |
Rights holder/Author | Leo Shapiro, Leo Shapiro |
Source | No source database. |
Rounded Global Status Rank: GNR - Not Yet Ranked
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Pyrus+calleryana |
Callery pear was imported multiple times to the U.S., including the first introduction in 1909 to the Arnold Arboretum and an introduction in 1916 by the U.S. Department of Agriculture for development of fire blight resistance in the common pear (Pyrus communis), which was devastating the commercial pear industry. It was widely planted as a rootstock for common pear long before it gained interest as an ornamental. Around 1950, the ornamental value and hardiness of Callery pear were recognized, leading to the development of a number of cultivars, including ‘Bradford.’ Cultivars in the U.S. originated from China and represent different genotypes. While some genotypes are self-incompatible, meaning they require cross pollination from another genotype in order to set seed, others can pollinate themselves. Different genotypes growing near each other (e.g., within about 300 ft.) can cross-pollinate and produce fruit with viable seed. Also, cultivars are often grafted onto seed-grown rootstocks with varying genotypes; if the plant produces shoots from the rootstock (which it often does), then these shoots and the graft can pollinate one another. Thus, the Bradford pear cultivar is one of several cultivars (varieties) of Callery pear capable of spreading and being invasive. Pyrus calleryana ‘Bradford’ is one genotype. It is propagated asexually (by grafting and cuttings) and does not change over time. Any plant resulting from a seed produced by Pyrus calleryana ‘Bradford’ is a different genotype of Pyrus calleryana and not a member of any cultivar (unless somebody propagates that seedling and names it as a new cultivar). The plants that spread in natural areas are not cultivars. They are sexually reproducing populations consisting of multiple genotypes that recombine every generation.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | U.S. National Park Service |
Source | http://www.nps.gov/plants/alien/pubs/midatlantic/pyca.htm |
Do not plant Callery pear or any cultivars including the well known Bradford pear. Seedlings and shallow-rooted plants can be pulled when soil is moist. Medium to large trees should be cut down and stumps treated with a systemic glyphosate or triclopyr-based herbicide.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | U.S. National Park Service |
Source | http://www.nps.gov/plants/alien/pubs/midatlantic/pyca.htm |
While the Callery Pear is an attractive landscape tree, it may eventually become as much of a pest as Morus alba (White Mulberry) and Elaeagnus umbellata (Autumn Olive). Another common name of Pyrus calleryana is 'Bradford Pear,' which refers to a widely planted cultivar of this species. Because an old cultivar of the Table Pear, Pyrus communis, is also called 'Bradford Pear,' this common name is potentially misleading. The Table Pear, which is cultivated for its edible fruit, is similar in appearance to the Callery Pear. However, both its flowers and pear-shaped fruit are larger in size.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/callery_pear.htm |
This small tree adapts to full or partial sun, moist to dry-mesic conditions, and soil containing loam, clay-loam, or sand. The pH of the soil can be acid to alkaline. Winter cold is tolerated to Zone 5. The Callery Pear is fast-growing, but rather short-lived (30-50 years); its branches are prone to ice and storm damage.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/callery_pear.htm |
This introduced tree is 20-50' tall with multiple ascending branches; the crown is usually longer than it is wide. The gray bark of the central trunk has shallow furrows and flat scaly ridges; it is often partially covered with lichens. The bark of smaller branches and twigs is greyish or reddish brown and smooth with small lenticels. The terminal buds of the twigs are rather large (about ½" long) and usually pubescent; sometimes thorny spur shoots are present. The blades of the alternate leaves are 2-3" long and about half as much across; they are ovate with margins that are finely serrate or crenate. The upper surfaces of the blades are dark green, hairless, and shiny; their lower surfaces are pale green and dull. The petioles of the leaves are 1-2" long, light green, and slender. During the mid-spring, clusters of several white flowers develop from the axils of young leaves; these flowers often appear shortly before the leaves develop. The pedicels of the flowers are slender and ascending to slightly drooping. Each flowers is ½¾" across, consisting of 5 white petals, a light green calyx with 5 teeth, 15-20 stamens, and 2-3 styles. Each fertilized flower produces a single globoid fruit (a pome) about 1/31/2" across. The exterior of a mature fruit is light brown with pale dots, while its fleshy interior contains about 2 seeds. Usually, the flavor of the fruit is bitter. On mature fruit, the teeth of the calyx are usually deciduous. Fall color of the leaves is variable as this depends on the cultivar.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/callery_pear.htm |
Once established Callery pear forms dense thickets that push out other plants including native species that can’t tolerate the deep shade or compete with pear for water, soil and space. A single tree can spread rapidly by seed and vegetative means forming a sizeable patch within several years. Its success as an invader results from its capacity to produce copious amounts of seed that is dispersed by birds and possibly small mammals, seedlings that germinate and grow rapidly in disturbed areas and a general lack of natural controls like insects and diseases, with the exception of fire blight.
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | U.S. National Park Service |
Source | http://www.nps.gov/plants/alien/pubs/midatlantic/pyca.htm |
So far, the Callery Pear has naturalized in DuPage and Champaign counties in Illinois (see Distribution Map). It seems likely that this species will continue to spread in the state; some ecologists think it is potentially invasive, as the wild trees produce abundant fruits with fertile seeds. So far, this tree has been found in various disturbed habitats, including degraded open woodlands, woodland borders, thickets, fence rows, and fallow fields. This habitat information has been compiled from several states in the eastern half of the United States, where the Callery Pear has naturalized. This tree is widely cultivated as an ornamental landscape plant and about 20 cultivars are available. While some cultivars are self-sterile, cross-pollination across cultivars can produce trees with fertile fruit. The Callery Pear is native to East Asia.
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | Copyright © 2002-2014 by Dr. John Hilty |
Source | http://www.illinoiswildflowers.info/trees/plants/callery_pear.htm |