Ivy (Hedera helix L., Araliaceae) is an abundant, evergreen, rootclimbing liana, widespread across most of Europe and western Asia (Schnitzler, 1995;Metcalfe, 2005). Its phenotype is mainly characterized by differences in the morphology and growth habits of the juvenile and adult phases (Jones, 1999;Metcalfe, 2005). Typically, juvenile plant stems initially grow as prostrate, plagiotropic shoots on the ground, and this phase can persist for a prolonged time (Wareing and Frydman, 1976). As they make contact with an adequate support, newly developed shoots grow as climbing axes, attached to the support via adventitious roots (Melzer et al., 2010(Melzer et al., , 2012. Juvenile shoots additionally occur in the form of "searchers" or vine tips-i.e., self-supporting tip regions of climbing axes (Gartner and Rowe, 2000). The adult phase of H. helix consists of orthotropic self-supporting shoots, which bear flowers and fruits for reproduction. Besides these differences in growth habits, the ontogenetic change from the juvenile to the adult reproductive phase is distinguished by other vegetative traits, for example, leaf shapelobed in juvenile and entire in adult phase (Stein and Fosket, 1969;Zotz et al., 2011), phyllotaxis-alternate in juvenile and helical in adult phase (Stein and Fosket, 1969;Poethig, 1990), and adventitious roots-present only in the juvenile phase (Stein and Fosket, 1969).Besides the relevance of H. helix to horticulture, including interest in its phase change, research on H. helix has focused mainly on its ecology (