Many species of Calamagrostis are morphologically similar, but they generally occur in distinct habitats, and they have unique geographical distributions. Given the subtle distinctions between many closely related taxa, there are several species complexes that could benefit from additional systematic study. Even the generic boundaries of the genus are controversial. For example, species in the genus Deyeuxia, distributed largely in the southern hemisphere are morphologically very similar to species of Calamagrostis. It may be appropriate to recognize all of these species in a single genus, but this will require detailed scientific study of DNA of species from around the world.
