While there is increasing world-wide discussion of the importance of renewable biological resources and a bio-based economy, science educators around the world have become aware of a declining general interest in plants and agriculture and of little knowledge of plants among the public. Recently, there have been few systematic investigations on the knowledge of crops. To address this observation, we initiated a questionnaire survey with secondary school students based on the assumption that students should acquire a fundamental knowledge of agriculture and crop-plant biology during compulsory education. As home is a source of information, parents were also questioned. On the whole, 926 German secondary school students aged nine to 18 years and 314 parents participated in our questionnaire survey. The data suggest an unsatisfactory level of knowledge about crop plants among students. Girls have greater knowledge and claim to be interested in crops more often than do boys. While knowledge of species was independent of grade and age, knowledge of crop use did increase with increased years of schooling. Parents showed an overall better performance than the students' on items involving plant recognition and their use.