Distribution and History of Naturalized Common Pear, Pyrus communis, in Ontario

Résumé

Considered rare or entirely overlooked until 1998, Pyrus communis is currently widespread and locally abundant as an escape from cultivation in southern Ontario. It was first noticed growing wild in Elgin County in 1949 and up until 1965 it was known as a wild plant only in the eastern Lake Erie region. It was first reported in the eastern Lake Ontario region in 1969 and is now widespread and locally abundant there. It now occurs north to the Georgian Bay region, and southwest to Essex County. Since it has had a very effective and rapid dispersal system for centuries as a result of cultivation and discarded cores, the apparently recent spread may be a consequence of climate warming extending the area within which it can grow wild, otherwise it would have escaped much earlier. It occurs in old fields and along fences within agricultural landscapes, but has been recorded in native woodland, prairie and alvar habitats. It dominates abandoned fields and pasture in some areas and may also increase in certain natural habitats and compete with native species. It is, however, less aggressive than some other alien woody plants and provides abundant food in the form of pollen, nectar and fruit during the early stages of old field succession. Spread is believed to be mostly by humans, but Racoons, deer, and other small mammals may be important in local dispersal.