Autoallelopathic potential of aqueous extracts from Canadian goldenrod (Solidago canadensis L.) and giant goldenrod (S. gigantea Aiton)

Production of allelopathic substances is a factor determining the ecological success of invasive plants—Canadian goldenrod (S. canadensis L.) and giant goldenrod (S. gigantea Aiton). This research aimed at evaluating the autoallelopathic effect of aqueous extracts (AEs) prepared from various parts of Canadian goldenrod and giant goldenrod against vegetative growth, and biomass accumulation of both goldenrods. In the stage of 5–6 leaves, goldenrod plants, were foliar sprayed with AEs, at concentrations of 5 or 10%. The biochemical properties of AEs, i.e., total phenolic content, total antioxidant potential and selected plant hormones, were examined. Two and ten days after spraying (DAS), damages to aboveground parts of goldenrods (necrosis and wilting) were visually assessed. The fresh mass of above- and belowground parts of goldenrods were measured 21 DAS. AEs from various parts of Canadian goldenrod or giant goldenrod displayed autoallelopathic properties of inhibitory nature. The phytotoxic potential of AEs varied depending on their source. Canadian goldenrod was more susceptible to the AEs, manifested by more significant damages to aboveground parts and a greater decrease in above- and belowground biomass. The most effective against growth and development of Canadian goldenrod and giant goldenrod were AEs from rhizomes, which caused a reduction of fresh biomass of goldenrods up to 42%, compared to water-treated control.