Plants are characterised by a great diversity of easily observed features such as colours or shape, but children show low interest in learning about them. Here, we integrated modern theory of adaptive memory and evolutionary views of the function of fruit colouration on children's retention of information. Survival-relevant (fruit toxicity) and survival-irrelevant information (naming and occurrence) about twelve plant species that differ in toxicity (toxic and non-toxic) and fruit colouration (red, green and black) were presented to a sample of Slovak high school students. Analyses of surprise retention tests immediately after a plant presentation and one week later showed that participants retained more information about plants with red and black fruits, compared with plants with green fruits. Survival-relevant information was retained significantly better than survival-irrelevant information and fruit's edibleness was associated with the colour red and toxicity was associated with the colour black. This study provides support for the existence of evolved memory mechanisms that enhance retention of survival-relevant information. Furthermore, it highlights the importance of fruit colouration as well as the type of information that children receive about plants on their cognitive processes.