Soreng's principal interest is in grasses (fam. Poaceae), and he specializes in the taxonomy of cool season grasses (Pooideae), particularly the genus Poa (ca. 500 species world-wide). Having spent 8 years conducting molecular research on relationships among grasses at family, subfamily, tribal and genus levels, he now devotes time to the study these plants in the herbarium and the field, while continuing to collaborate with colleagues on molecular studies. Poa possibly has the most variation in breeding systems of any genus of plants, and he studies this variation to better assess the nature of species in this genus. Soreng also specializes in grass nomenclature and helps to maintain and update the grass data in TROPICOS (Missouri Bot. Gards. taxonomic database).