Questions: Is dormancy selected as a means by which a seed defers germination until suitable environmental conditions occur? Are plant species in frost-free and drought-free environments less likely to have some form of dormancy than species from environments with frost and/or drought? Are there any relationships between dormancy and three important plant traits: seed size, plant longevity, and growth form?

Methods: Data from the literature including 3164 species were compiled. We quantified the relationship between dormancy and seed size (1795 species), plant longevity (183 species), and growth form (3164 species).

Results: Plant species of environments with frost and/or drought were more likely to possess some form of seed dormancy (morphological, physiological, morphophysiological, or physical) than species in more benign environments. Seeds exhibiting some form of dormancy were lighter in weight and generally more prevalent among herbaceous species. Woody plants had a larger proportion of non-dormant seeds. There was a broad overlap in seed size between species with dormant and non-dormant seeds. We also found no significant relationship between seed dormancy and plant longevity.