The biology of invasive alien plants in Canada. 10. Nymphoides peltata (S. G. Gmel.) Kuntze

Abstract

The freshwater aquatic species Nymphoides peltata has been introduced to Canada as an ornamental plant and has been found at sites in Newfoundland, Nova Scotia, Quebec, Ontario and British Columbia. It is currently available through the aquatic nursery trade in Canada and the United States. It may be considered as adventive in Canada since populations readily expand beyond the site of planting, but there is no evidence as yet that it is fully naturalized. In the United States it has naturalized in still or slow-moving waters at widely scattered locations where it replaces native plant communities, changes ecological processes and interferes with human navigation and recreational activities. The short rhizomes over-winter under Canadian conditions, even when complete water drainage results in freezing of the substratum. In its native range, the species has two floral morphs (i.e., is distylous) with a weak incompatibility system, but North American populations usually consist of a single flower morph. A population at Ottawa, ON, has monomorphic flowers with characteristics overlapping between the two Eurasian morphs and has been observed to produce large numbers of viable seeds. Seeds germinate in the spring either on the substratum in shallow water or at the water surface. Seedlings germinating at the water surface may float for several weeks prior to sinking and establishing on the substratum in shallow water. Vigorous stolon production promotes rapid colonization, and vegetative dispersal is readily accomplished through fragmentation of stolons and stems.