We investigated usability of mobile computers and field guide books with adult botanical novices, for the identification of wildflowers and deciduous trees in winter. Identification accuracy was significantly higher for wildflowers using a mobile computer app than field guide books but significantly lower for deciduous trees. User preference followed a similar pattern. These results suggest that the identification method and its design are more important for a field guide than its presentation medium (electronic or printed). We discuss the relative advantages of the presentation media used and their value as engagement tools for botany.