Ambrosia Cheiranthifolia is a rare member of the Asteraceae family known by the common names South Texas ambrosia, Rio Grande ragweed, and South Texas ragweed, is an erect perennial herb that spreads via underground rhizomes to form small colonies.

The plant features stems growing up to 16 inches tall with a distinctive foliage pattern where the leaves are arranged oppositely on the lower stem and transition to an alternate arrangement above. These sessile leaves are oblong-lanceolate to oblanceolate in shape, growing to about 2 inches long with entire margins, though younger leaves may occasionally be slightly pinnately lobed. Both the leaves and stems have surfaces covered in short, appressed hairs that contribute to the plant’s texture.

During its blooming period, which spans spring, summer, and fall, it produces small, greenish male and female flowers separately on a terminal inflorescence, with the male flowers extending prominently above the clustered female flowers nestled below. This rare species is restricted to a handful of counties along the southern coast of Texas, south of the Coastal Bend region, where it inhabits open fields, native prairies, and open shrublands (1).