Achene traits involved in the water dispersal of the invasive Fallopia × bohemica complex: Variability and dispersal strategies

•The floatability of F. x bohemica achenes varies from 2.5 to 5 days.•The emergence of floating seedlings extends this period to 20 days.•Germination proportions vary from 0.3 to 0.95 between stands.•They are negatively related to the median germination time.