Science education encounters a number of obstacles to its progression. Among them are preconceptions or misconceptions, which can be persistent even among teachers. In order to find out what are these preconceptions o misconceptions about plants of future primary school teachers, the present research was carried out. A questionnaire was used during three academic years to collect information from pre-service teachers. Among the results, incomplete knowledge of plant biology and serious errors in relation to plant nutrition stand out. This seems to indicate the need to change traditional methodologies and use other active methodologies that allow future teachers to have real contact with the living beings in their environment.