Hymenothrix, commonly known as thimbleheads, is a small genus of flowering plants in the family Asteraceae (daisy family), order Asterales. The genus was described by Asa Gray and comprises roughly 10–11 species of annual, biennial, and perennial herbs native to the arid and semi-arid regions of the southwestern United States and northern Mexico.
Plants in this genus are characteristically spindly and erect in habit, bearing small flower heads with white or yellow ray or disc florets. The common name "thimbleheads" likely refers to the compact, thimble-like appearance of the flower heads.
The genus is distributed across a wide swath of the Chihuahuan and Sonoran Desert borderlands, with species ranging from California, Nevada, Utah, Colorado, and South Dakota in the north, through Arizona, New Mexico, and Texas, and south into the Mexican states of Baja California, Sonora, Chihuahua, Coahuila, and Nuevo León. Notable members include Hymenothrix wislizeni (Trans-Pecos thimblehead), found in the Trans-Pecos region of Texas and adjacent Mexico, and Hymenothrix dissecta, which has the widest range in the genus spanning both sides of the US–Mexico border.
Distribution
Hymenothrix is native to the southwestern United States and northern Mexico. Species occur across Arizona, New Mexico, Texas, California, Nevada, Utah, Colorado, and South Dakota, and extend south into the Mexican states of Chihuahua, Sonora, Baja California, Coahuila, Nuevo León, and México State. The genus is centered on the Chihuahuan and Sonoran Desert regions.
Taxonomy Notes
The genus Hymenothrix was described by Asa Gray and is placed in the family Asteraceae (Compositae), order Asterales. Some taxonomic sources formerly included Hymenothrix purpurea Brandegee, now treated as Florestina purpurea (Brandegee) Rydb.
