The Beginning of a New Invasive Plant: A History of the Ornamental Callery Pear in the United States

The Callery pear (Pyrus calleryana Dcne. [Rosales: Rosaceae]), an ornamental tree from China, has begun appearing in disturbed areas throughout the United States. To understand the relatively recent spread of this species into natural areas, we review its horticultural history, the traits promoting...

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Bibliographic Details
Published in:Bioscience 2007-12, Vol.57 (11), p.956-964
Main Authors: CULLEY, THERESA M, HARDIMAN, NICOLE A
Format: Article
Language:English
Subjects:
agricultural history
Alien plants
Botanical gardens
Callery pear
colonizing ability
cultivar
Cultivars
Environmental economics
Flowers & plants
Fruits
genotype
Genotypes
History
hybridization
intraspecific hybridization
Introduced plants
Introduced species
Invasive plants
Invasive species
invasiveness
Nonnative species
Ornamental trees
OVERVIEW ARTICLES
parks
Pear
Pears
plant density
plant ecology
Plant introduction
plant reproduction
Plants
provenance
Pyrus
Pyrus calleryana
residential areas
Rootstocks
Rosaceae
Rosales
seed dispersal
Seedlings
Seeds
self-pollination
Street trees
traits
Trees
Urban areas
Varieties
wetlands
wild birds
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Summary:The Callery pear (Pyrus calleryana Dcne. [Rosales: Rosaceae]), an ornamental tree from China, has begun appearing in disturbed areas throughout the United States. To understand the relatively recent spread of this species into natural areas, we review its horticultural history, the traits promoting its invasiveness, and its current invasive status. Cultivated varieties (cultivars) of this species sold in the United States originate from different areas in China and represent genotypes that have been planted in high densities in residential and commercial areas in the introduced range. The species cannot self-pollinate because of a self-incompatibility system, but recent fruit set is due to crossing between different cultivars or between the scion and rootstock of cultivated individuals. Consequently, individual cultivars themselves are not invasive, but the combination of cultivars within an area creates a situation in which invasive plants can be produced. Because of the established nature of this species in urban areas, the spread of wild P. calleryana will most likely continue, especially as new cultivars continue to be introduced into the mixture of cultivars already present.
ISSN:0006-3568
1525-3244
DOI:10.1641/B571108