An increase in the number of citizen science programs has prompted an examination of their ability to provide data of sufficient quality. We tested the ability of volunteers relative to professionals in identifying invasive plant species, mapping their distributions, and estimating their abundance within plots. We generally found that volunteers perform almost as well as professionals in some areas, but that we should be cautious about data quality in both groups. We analyzed predictors of volunteer success (age, education, experience, science literacy, attitudes) in training-related skills, but these proved to be poor predictors of performance and could not be used as effective eligibility criteria. However, volunteer success with species identification increased with their self-identified comfort level. Based on our case study results, we offer lessons learned and their application to other programs and provide recommendations for future research in this area.