suckering, Vegetative formation of a new stem and root system from an adventitious bud of a stem or root, either naturally or by human action. Such asexual reproduction is based on the ability of plants to regenerate tissues and parts. Examples of plants that spread by suckers include red raspberry, forsythia, and lilac. Suckering allows horticulturists and agriculturists to reproduce a desired plant over and over without significant variation.