Woolly nightshade (Solanum mauritianum) and its allelopathic effects on New Zealand native Hebe stricta seed germination.

Solanum mauritianum Scop., an exotic tree commonly known in New Zealand as woolly nightshade, is classified as a national surveillance plant pest. Woolly nightshade is extremely invasive and can out-compete surrounding flora due to its fast reproduction cycle, large annual seed mass and rapid growth rates. Groves of woolly nightshade commonly lack understorey vegetation, generally believed to be caused by shading out effects. Trials investigating possible allelopathic effects of woolly nightshade on seed germination of the native shrub Hebe stricta were carried out over a 22-day period. In this trial, seeds were germinated on filter paper saturated with various concentrations of woolly nightshade leaf, stem and root leachates or rainwater. Rainwater was used as a control treatment to simulate field conditions. Results show woolly nightshade does have significant allelopathic effects: 54% of seeds treated with rainwater germinated compared to 0% of seeds treated with 100% leafleachate concentration.