THE BIOLOGY OF CANADIAN WEEDS.: 69. Potamogeton crispus L.

Abstract

A review is provided of information on the biology of curly-leaved pondweed (Potamogeton cripsus L.). This submersed aquatic behaves as a winter annual through the production of summer-dormant apices. These germinate in the fall giving rise to an overwintering plant with narrow, acute, flat-margined leaves. In spring, the winter foliage disintegrates and larger leaves with serrulate, undulate margins and round tips begin to develop. Fruit is produced and the development of dormant apices is completed mostly by late June, after which the plants begin to die and dormant apices sink to the bottom. An introduced species, curly-leaved pondweed had spread through much of the U.S. by 1950. It is now well established in southern Ontario and is one of the province’s major nuisance aquatics. It is also well established in Quebec, but is not a nuisance there and is not spreading (C. Hamel, pers. commun.). In contrast it is spreading rapidly in western Canada where it was first noticed only 20 yr ago. Curly pondweed has potential uses in waterfowl management and compositing. It thrives in alkaline, calcareous and polluted waters. The dormant apices are the most important mode of reproduction with up to 900 being produced by a single plant in 1 year. Where the plant is a problem in Ontario, mechanical harvesting techniques of control have been used effectively. Dominance of curly-leaved pondweed in some areas is probably a consequence of its unusual vegetative life cycle allowing competition avoidance, and its tolerance of polluted water.Key words: Potamogeton crispus, weed biology, Canada, distribution