Background and Aims:

The genus Podagrostis includes 12 species, formerly included in Agrostis, and until recently, only the existence of three species was known from Mexico. The examination of herbarium specimens revealed the presence of a fourth species, previously known only from Guatemala. The aim of this work is to describe and illustrate the new record, and to discuss the identity of the examined specimen and the morphological differences of this species with the other Mexican species.

Methods:

Herbarium specimens of Agrostis and Podagrostis of Mexico and Central America, from physical and digital collections, were examined and photographs of important reproductive structures for identification were taken.

Key results:

Podagrostis exserta is recorded here for the first time in Mexico, in the state of Oaxaca. The identity of the examined specimen and the differences of this species with other Mexican species of Podagrostis are discussed. A dichotomous key is presented to differentiate them.

Conclusions:

The genus Podagrostis is now represented in Mexico by four species, P. exserta, P. liebmannii, P. novogaliciana and P. rosei, distinguishable from Agrostis by spikelets with a prolonged rachilla. The importance of curatorial work of Mexican herbaria collections is highlighted.