Our understanding of stomatal development in Arabidopsis thaliana is based on mutants with aberrant, often lethal phenotypes. Through a comprehensive analysis of stomatal abundance in wild A. thaliana accessions, Delgado et al. determine relationships amongst stomata-related traits and uncover hidden genetic variation in stomata developmental pathways. The study identifies natural accessions with extreme or uncommon phenotypes as resources for the genetic dissection of this developmental process.