Hymenothrix wislizeni, Trans-Pecos Thimblehead
Scientific Name: Hymenothrix wislizeni
Common Name: Trans-Pecos Thimblehead
Also Called: TransPecos Thimblehead
Family: Asteraceae, Sunflower Family
Synonyms: ( )
Duration: Annual or biennial.
Size: Up to 3 feet.
Growth Form: Forb/herb, subshrub; multiple upright slender green stems, branching near the top.
Leaves: Green, alternate, leaves more dense near the bottom of stems; simple pinnately divided into 3 narrow linear lobes (middle-left photo); leaf margins slightly turned in or revolute.
Flower Color: Yellow; ray flowers, disk flowers and anthers yellow; ray flowers with 3 to 8 florets; disk flowers with 15 to 30 florets; flower heads numerous in terminal clusters; fruit is an achene.
Flowering Season: June to December.
Elevation: 2,500 to 5,500 feet.
Habitat Preferences: Sunny open areas, plains, mesas, washes, sandy and gravelly soils.
Recorded Range: Relatively rare in the United States Trans-Pecos Thimblehead is found only in AZ, NM and TX. It is also found in Baja California and northern Mexico. In Arizona; Yavapai County and the southern half of Arizona excluding the southwest corner. New Mexico it is found in the southwest corner and two isolated populations. Texas is poorly represented with only a few specimens recorded.
U.S. Weed Information: No data available.
Invasive/Noxious Weed Information: No data available.
Wetland Indicator: No data available.
Threatened/Endangered Information: No data available.
Comments: Trans-Pecos Thimblehead is similar in appearance to both Wright’s Thimblehead, Hymenothrix wrightii and Loomis' Thimblehead, Hymenothrix loomisii. The most obvious differences are in the flowers both Wright’s and Loomis’ Thimblehead flowers are discoid only without the ray flowers found on Trans-Pecos Thimblehead.
Other differences are in the flower colors, Wright’s Thimblehead flowers have white or pinkish corollas and pinkish anthers and Loomis' Thimblehead has cream or yellow flowers but again, they lack the ray flowers found only on Trans-Pecos Thimblehead. Middle-right small photo above shows cypsela seed and pappi.