1. Plant biodiversity, which is fundamental for the delivery of ecosystem services, is in decline. Yet, knowledge about how plant biodiversity is perceived and appreciated is scarce.2. We studied biologists' and laypeople's perception and appreciation for plant communities that differ in plant biodiversity, using ranges of plant biodiversity known to affect ecosystem services. We investigate species richness, species turnover and species evenness. A questionnaire based on photographs displaying artificial plant communities was used.3. Perceived biodiversity was 12% more often congruent with actual biodiversity for biologists than for laypeople. Species richness was perceived congruently with actual species richness by 77% of all respondents, compared with 27% for species evenness and 29% for species turnover. Appreciation for the displayed communities correlated positively with their actual plant biodiversity, except for species turnover. Appreciation always correlated positively with perceived plant biodiversity and even stronger than with actual plant biodiversity. This was not the case for species richness, for which perceived and actual biodiversity were most often congruent. 4. Our results suggest that plant biodiversity is perceived most accurately when changes in species richness are considered, while changes in species evenness and species turnover are perceived less accurately. The respondents' answers indicate that perceived higher plant biodiversity is appreciated more than perceived lower plant biodiversity, even when perceived and actual plant biodiversity are not congruent. 5. We corroborate findings that people value plant biodiversity per se. But we also find that people largely perceive species evenness and turnover with low accuracy; and that people have low appreciation for these biodiversity dimensions that are lesser known but essential to ecosystem functioning. Our finding that biologists have higher accuracy in perceiving biodiversity suggests that biodiversity literacy is key to increasing people's awareness of changes in plant biodiversity.