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| Callery Pear | ||||||||||||||
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 Callery Pear fruit in autumn
 Callery Pear blossoms
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| Pyrus calleryana Decne. |
The Callery Pear (Pyrus calleryana) is a species of pear native to China. It is a deciduous tree growing to 15-20 m tall, with a conic to rounded crown. The leaves are oval, 4-7 cm long, glossy dark green above, slightly paler below. The flowers are produced in early spring before the leaves expand fully, and are white, with five petals, and about 2-3 cm diameter. They have a sickly-sweet smell.
The fruit is less than one cm in diameter, hard, almost woody until softened by frost, after which it is readily taken by birds, which disperse the seeds in their droppings. In summer, the foliage is dark green and very smooth, and in autumn the leaves commonly turn brilliant colors, anything from yellow and orange to more common red, pink, purple, and bronze. Sometimes, several of these colors may be present on an individual leaf. However, the color often occurs very late in fall, and the leaves may be killed by a hard frost before full color can develop.
This tree is amazingly resistant to sicknesses or blight, and is killed more often by storms and high winds than by sickness.
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Cultivation
It is so widely planted throughout North America as an ornamental tree that the tree (specifically the Bradford Pear) has become a ubiquity in many suburban communities. It is tolerant of a variety of soil types, drainage levels and soil acidity. Its shape varies from ovate to elliptical. The symmetry of several cultivars lends to their use in somewhat formal settings, such as office parks or industrial parks. It is commonly planted for its decorative value, but its hard little fruits are taken by birds. Its beautiful white blossoms can be seen in early spring along the boulevards of many eastern U.S. towns. At the latitude of Pittsburgh, PA the trees often remain green until mid-November, and in warm autumns, the colors are often a brilliant end to the fall color season, while in a cold year they may get frozen off before coloring. In the South, they tend to be among the more reliable coloring trees.
Invasive species
The Callery Pear is proving to be an invasive species in some areas of North America, pushing out native American plants and trees. Seedling plants often differ from the selected cultivars in less regular shape, and also in frequently being densely thorny. In a paper in the botanical journal Castanea, Vincent (2005) reported the species as an escape in 152 counties in 25 states in the United States.
Cultivars
There are several cultivars in commerce, including 'Aristocrat', 'Autumn Blaze', 'Bradford' (Bradford Pear, the most commonly planted cultivar), 'Capital', 'Cleveland Select', 'New Bradford', 'Redspire', and 'Whitehouse'.
The neat, dense upward growth of 'Bradford' — which makes it desirable in cramped urban spaces — also results in a multitude of narrow, weak forks, unless corrected by selective pruning at an early stage. These weak crotches make the Bradford Pear very susceptible to storm damage where snowfall is heavy or when ice storms occur, or during the high winds of severe thunderstorms. Because of this, and the relatively short lifespan that results (typically less than 25 years), many groups have discouraged their use in landscaping in favor of other stronger trees including other Callery Pear cultivars like 'Cleveland Select', but also encourage the use of more locally native tree species.
Uses by humans
Callery pear can be used as rootstock for grafting pear cultivars such as Comice, Bosc, or Seckel and especially for nashi pear.
References
- Vincent, M.A. (2005). "On the spread and current distribution of Pyrus calleryana in the United States". Castanea 70: 20–31. doi:.
External links
- Plant Invaders of Mid-Atlantic Natural Areas
- Pyrus calleryana images at bioimages.vanderbilt.edu
- "Scientists Look for Clues Into How Tree Populations Become Invasive" Jan 15, 2008 by Stacy Kish, CSREES Staff.
Wikipedia content modification information:
- This page was last modified on 10 November 2008, at 17:16.
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