A rare plant that can be found in the Rio Grande Valley is now being considered for endangered species status.

Between Starr and Zapata counties, experts have identified 671 acres where the prostrate milkweed grows.

"You have plants that occur in Starr County that don't occur anywhere else in the United States,"  said Joey Santore, a Chicago native and self-taught botanist who often visits the Valley for his video series, ‘Crime Pays, but Botany Doesn’t.’

The U.S. Fish and Wildlife Service is proposing to list the prostrate milkweed, a host plant for the struggling monarch butterfly, as endangered under the Endangered Species Act.

Santore says he's seen county workers mow the plants down.

"I mean these are tough plants," Santore said. "They're tough in terms of dealing with drought and lack of nutrients, but they're not tough when it comes to being scraped away by humans."

In a news release, the U.S. Fish and Wildlife service said "border security enforcement" and the spread of the invasive buffelgrass has also hurt the plant's growth. 

"Literally a surveyor stake...with all those plastic fibers coming out. Neon plastic blue fibers," Santore said. "There was literally a surveyor stake right next to a asclepias prostrata, right next to this prostrate milkweed. And, so the wall would literally go right on top of these plants."

If approved, the endangered species law could limit future construction. 

Public comments are being accepted until April 18.