More than a century ago, Goebel (1889) described these species as "heteroblastic" to be distinguished from "homoblastic" taxa, in which changes are negligible or gradual.
The term "heteroblastic" (condition: 'heteroblasty') [from Greek blastos, shoot] was originally introduced by Goebel to describe a form of plant development, in which substantial differences between earlier ("Jugendform" = juvenile form) and later stages ("Folgeform", subsequent form) are observed as opposed to the "homoblastic" type of development with small and gradual changes (Goebel, 1898, 1913).
The major advance achieved with this scheme is the possibility of a quantitative distinction between homoblastic and heteroblastic species, morphologically or physiologically, which overcomes the vagueness of Goebel's definition (see below).
Ray's (1990) system, originally proposed for heteroblastic vines, allows a clear distinction between homoblastic and heteroblastic species.
Trees can show small, gradual changes from juvenile to mature states (homoblastic
), or they can exhibit an abrupt transition (heteroblastic), as found in Quercus, Robinia, and Eucalyptus.