Response of Pale Swallow-wort, Vincetoxicum rossicum, following Aboveground Tissue Loss: Implications for the Timing of Mechanical Control

Résumé

The growth and reproduction of Pale Swallow-wort, Vincetoxicum rossicum, were investigated following differentially timed above-ground tissue loss by clipping throughout the growing season in Ottawa, Canada. If clipping occurred early in the growing season (before June), mature plants were able to compensate in height but not in biomass or reproductive output when compared to uncut controls. This compensation in height did not seem to come at the expense of below-ground storage tissue; there was no significant difference in root mass among the control and treatment conditions. Final plant height, mass, and reproduction declined as plants were cut later in the season. Pale Swallow-wort seedlings clipped before June were able to compensate in height when compared to uncut controls. Unlike mature plants, this compensation in height did come at the expense of root mass. As the clipping treatment was performed later into the growing season, both final plant height and shoot mass decreased, while root mass increased. The best time for controlling the population spread of Pale Swallow-wort using a single cutting treatment was on or near 26 June. Plants cut earlier than this date were able resprout and produce seeds; those cut after had already produced seeds that appeared viable and may be able to germinate if the cut stems were left in the field. When a single cutting or mowing treatment is to be employed for controlling Pale Swallow-wort, we recommend cutting after the first fruits are produced but before they are fully developed.