This grounded theory study explored the pedagogical content knowledge (PCK) of experienced agriculture teachers in the plant sciences. The most emergent phenomenon to surface from the data was the influence of beliefs on participants' PCK. This central phenomenon became the cornerstone for the model of what was shaping experienced agriculture teachers' PCK in the plant sciences. The three major components that shaped the participants' PCK were: integrated belief systems, experiences prior to and during inservice, and the influence of the school and community context. A substantive level theory was developed that illustrated relationships between these three main components and their impact on participants' PCK. Recommendations from this study include conceptualization of experienced agriculture teachers' PCK for a variety of agriculture topic areas and exploration into the development of PCK in preservice and beginning teachers.