Author
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Whittemore, Alan |
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Submitted to: Journal of Botanical Research Institute of Texas
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/9/2008 Publication Date: 7/11/2008 Citation: Whittemore, A.T. 2008. Exotic species of Celtis (Cannabaceae) in the flora of North America. Journal of the Botanical Research Institute of Texas. 2:627-632. Interpretive Summary: Two non-native species of hackberry, Celtis australis and C. sinensis, are shown to be escaping and naturalizing locally in areas of the United States where they are planted as ornamental trees. Celtis australis is a weed in heavily disturbed sites in the Sacramento Valley of California, and it is reproducing in native riparian woodland at one site in Chico, California. Celtis sinensis, which has never been reported to escape in North America, is shown to be reproducing outside of cultivation in a variety of habitats throughout California and in the District of Columbia. Neither species is aggressively invasive at any known site, but C. sinensis is able to disperse effectively over long distances, and seedlings are often found up to 300 m from adult plants. There is almost no published data on the ecology of these species in North America and no detailed descriptions or other identification aids in the North American floristic literature. The current range and habitat preferences of these trees in North America are summarized, and identification aids (full botanical descriptions and illustrations) are supplied for both species. This contribution updates our information on exotic tree species that escape from cultivation in the U. S., and provides aids for identification of these plants. It will be used by professional land managers, educators, conservationists, and sophisticated amateur botanists and horticulturalists, insuring that work on land management and conservation will be based on full, accurate and up-to-date information about the occurrence of these organisms in the United States. Technical Abstract: Two non-native species of Celtis, C. australis and C. sinensis, are shown to be escaping and naturalizing locally in areas of the United States where they are planted as ornamental trees. Celtis australis is a weed in heavily disturbed sites in the Sacramento Valley of California, and it is reproducing in native riparian woodland at one site in Chico, California. Celtis sinensis, which has never been reported to escape in North America, is shown to escape in a variety of habitats throughout California and in the District of Columbia. Neither species is aggressively invasive at any known site, but C. sinensis is able to disperse effectively over long distances, with seedlings often found up to 300 m from adult plants. There is almost no published data on the ecology of these species in North America and no detailed descriptions or other identification aids in the North American floristic literature. The current range and habitat preferences of these species in North America are summarized, and identification aids (full taxonomic descriptions and illustrations) are supplied for both species. The data supplied here on the habitats in which these Celtis species escape from cultivation in the United States, and the evidence for long seed dispersal distances in C. sinensis, helps to identify sites where these ornamentals should not be used, and the identification aids provided will allow accurate identification of the species so that their status can be monitored in the future. |
