Excerpts from Jim Conrad's
Naturalist Newsletter

from the August 28, 2016 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán MÉXICO
RUSTYSEED PASPALUM

On very thin soil atop limestone bedrock, on a shadowy trail through the woods at Hacienda Chichen, a grass was at its flowering peak. The trail at that point was so dark a flash was need to get the picture shown below:

Rustyseed Paspalum, PASPALUM LANGEI

Even at a distance you can see that this is one of those grasses that arranges its spikelets on narrow spikes or spike-like racemes atop the stem, like crabgrass and Bermuda grass. Up close, we see that, also like them, the florets are aligned along only one side of the flattened secondary inflorescence branches, or rachillas, as shown below:

Rustyseed Paspalum, PASPALUM LANGEI, spikelets with wing

Even closer, we see that each spikelet is only about 2mm long (0.08inch), consists of only one floret, is broadly oval, and that the coverings of the grains are hairy and bear three prominent veins on their flat sides, as seen below:

Rustyseed Paspalum, PASPALUM LANGEI, spikelets

In grass identification it's important to notice the ligule -- the wall-like structure where the blade meets the stem, and which can take any number of forms, when it's present at all -- and that's shown below:

Rustyseed Paspalum, PASPALUM LANGEI, ligule

There we're seeing the ligule consisting of two dark, papery, ear-like appendages surrounded by long, stiff, white hairs.

These features and others lead us to PASPALUM LANGEI, which at least the USDA calls Rustyseed Paspalum. It's native from Texas and Florida south through Mexico to northern South America, found in variously open areas, from forest trails like ours, to roadsides. It's listed as a livestock food, plus any small, seed-eating bird will be glad to pec at those plump grains.