The generic groups of the Tribe Stipeae are similar in many ways--often called the "needlegrasses." Hesperostipa comata and New Mexican Needlegrass are distinctive for their exceedingly long awns. Of these two, New Mexican Needlegrass awns have longer hairs, the basal part of the awn looking furry. When mature, the awns become bent and curly--see one up close by pulling it out of the glumes.
You won't likely confuse it with Tanglehead, which also
has twisted awns, because Tanglehead's seedheads appear dark brown. Tanglehead's awns
Next, eliminate the long, furry awns of New Mexican Needlegrass.
Now eliminate Desert Needlegrass, Pappostipa speciosa, (formerly Jarava speciosa).
Its 3-inch awns are are distinctly shorter and the awn's basal segment has very long hairs.
Achnatherum species have simelar floret shapes but are all much smaller and with
much shorter awns. Two exceptions are Mormon Needlegrass in northern Arizona and
Southwestern Needlegrass in the south. Both of these have 3-inch awns but the
florets to which the awns attach are only about 1/4 inch.