The French project Data to Knowledge in Agronomy and Biodiversity (D2KAB) will make available a semantically-enabled French agricultural alert newsletter. In order to describe/annotate crop phenological development stages in the newsletters, we need a specific semantic resource to semantically represent each stages. Several scales already exist to describe plant phenological development stages. BBCH, considered a reference, offers several sets of stages –one per crop called ’individual scales’– and a general one. The French Wine and Vine Institute (IFV) has aligned several existing scales in order to identify the most useful grapevine development stages for agricultural practices. Unfortunately these scales are not available in a semantic form preventing their use in agricultural semantic applications. In this paper, we present our work of creating an ontological framework for semantic description of plant development stages and transforming specific scales into RDF vocabularies; we introduce the BBCH-based Plant Phenological Description Ontology and we illustrate this framework with four scales related to grapevine.