The two subspecies differ in the occurrence of glandular depressions below culm nodes, spikelet color, and plant size.

[2] Eragrostis mexicana is a densely tufted annual growing 10–130 cm (3.9–51.2 in) tall, with slender culms that are either simple or loosely branching.

The ellipsoid to ovoid panicle is very lax and open, growing 4–20 cm (1.6–7.9 in) long (usually less than half the height of the total plant), with the spreading and ascending floral branches bearing scattered spikelets.

[3] Eragrostic mexicana can be found in disturbed areas such as waste places and road verges, or on dry hills and mountains.

[5] It grows from Iowa and Delaware down to southwest American states and Mexico, advancing as far south as Argentina, Brazil, and Paraguay, sometimes in lomas regions.