Aristida portoricensis is a rare species of grass known by the common name pelos del diablo ("hair of the devil").

It is endemic to Puerto Rico, where it is known from two locations, one in a residential area of Mayagüez and one in the Sierra Bermeja.

This is a perennial grass producing a tuft of stems up to 30 to 50 centimeters tall.

Its habitat includes subtropical wet forests and grassland on soils of clay and serpentine origin.

[2] Development of the Sierra Bermeja is a potential threat for the grass and many other endemic plant species.