In a five-year longitudinal study, 25 pupils were interviewed individually at the age of 10y, 11y, 13y and 15 years of age about the role of flowers in plant reproduction. At age 15, each pupil listened to what they had said four years earlier and described how they thought their understanding had developed. All interviews were tape-recorded and the audiotapes transcribed verbatim. Analysis of the interview data and the descriptions of the pupils’ differential conceptual development were grounded in Ausubel’s theory of meaningful learning. At the beginning of the study the pupils expressed human-centred ideas. They commonly used anthropomorphic and teleological reasoning to explain the flower’s role in plant reproduction. Each pupil’s conceptual development from ages 11 to 15 could be described by one of four categorisations. Six pupils expressed alternative ideas all of the interviews. Many pupils had undifferentiated ideas of pollination and seed dispersal. Conceptions of the role of the flower in plant reproduction at age 10y were used as a basis for later conceptual development. An early introduction of some scientific concepts can help students develop deeper understandings of ecological processes. It is important to illuminate pupils’ expressions and ideas of science phenomena, give them opportunities to reflect on their ideas and encourage them to compare their conceptualisations with other explanations.