The entire developmental cycle of the plants is subdivided into ten clearly
recognizable and distinguishable longer-lasting developmental phases. These
principal growth stages are described using numbers from 0 to 9 in ascending
order (see Figures 1a and b). The principal growth stages are described
in Table 1. Owing to the very many different plant species there may be shifts
in the course of the development or certain stages may even be omitted.
The principal growth stages need not proceed in the strict sequence
defined by the ascending order of the figures, but can occasionally also
proceed in parallel.