Hymenothrix wislizeni, Trans-Pecos Thimblehead, Southwest Desert Flora

Hymenothrix wislizeni, Trans-Pecos Thimblehead

Trans-Pecos Thimblehead has yellow flowers in terminal clusters. The flower heads have both ray and disk florets. The ray florets are generally 3-toothed. Hymenothrix wislizeni

Trans-Pecos Thimblehead flowers have yellow anthers arising from the middle of the florets. The fruit is referred to a cypsela. Hymenothrix wislizeni

Trans-Pecos Thimblehead flowers bloom from June or July to October, November and December depending on the weather particularly the summer monsoon rainfall. Hymenothrix wislizeni

Trans-Pecos Thimblehead grows from 2 to 3 feet (61-91 cm) tall, more or less. Hymenothrix wislizeni

Trans-Pecos Thimblehead bracts surrounding the floral heads, also called phyllaries, are generally linear in shape as shown in the photo. Hymenothrix wislizeni

Trans-Pecos Thimblehead leaves are green and most of the leaves are found at the base of the plant. Leaves are divided into 3 linear segments or linear lobes. Note that the leaf edges are rolled back or revolute. Hymenothrix wislizeni

Trans-Pecos Thimblehead fruit is called a cypsela which has a fuzzy pappus as shown in the photo. Hymenothrix wislizeni

Trans-Pecos is relatively rare in the United States where it is found only in AZ, NM and TX. It is also native in Baja California and northern and central Mexico. Thimblehead wislizeni

Scientific Name: Hymenothrix wislizeni
Common Name: Trans-Pecos Thimblehead

Also Called: TransPecos Thimblehead

Family: Asteraceae, Sunflower Family

Synonyms: ()

Status: Native

Duration: Annual or biennial.

Size: 2 to 3 feet (61-91 cm) tall more or less.

Growth Form: Forb/herb; multiple upright slender green stems, branching near the top.

Leaves: Green; majority of the leaves at the base of the plant; leaves are divided (dissected) into 3 linear segments or linear lobes (ternate); leaf edges or margins slightly rolled back (revolute).

Flower Color: Yellow; the yellow flowers are in terminal clusters; flower heads have both ray (8 to 12 yellow 3-toothed) and disk (15 to 30 yellow or cream) florets; bracts (phyllaries) surrounding flower heads linear; in the middle of the flowers are yellow anthers; fruit is a cypsela.

Flowering Season: June or July to October, November and December

Elevation: 2,000 to 5,500 feet (610-1,676 m).

Habitat Preferences: Sunny open areas, plains, mesas, along washes, roadsides, sand, gravelly and calcareous soils.

Recorded Range: Relatively rare in the United States where it is found only in AZ, NM and TX. It is also native in Baja California and northern and central Mexico. In the southwestern United States it is found mostly in the central and southern parts of Arizona; there are a few disjunct populations in New Mexico and Texas is poorly represented with only a few specimens recorded in the far west.

North America & US County Distribution Map for Trans-Pecos Thimblehead, Hymenothrix wislizeni.

North America species range map for Trans-Pecos Thimblehead, Hymenothrix wislizeni:
North American range map courtesy of Virginia Tech, Dept. of Forest Resources & Environmental Conservation

Click image for full size map

U.S. Weed Information: Unknown
Invasive/Noxious Weed Information: Unknown
Wetland Indicator: Unknown
Threatened/Endangered Information: Unknown

Genus Information: In North America there are 3 species and 3 accepted taxa overall for Hymenothrix. Worldwide, The Plant List includes 6 accepted species names and a further 10 scientific names of infraspecific rank for the genus.

The genus Hymenothrix was published by Asa Gray, (1810-1888), in 1849.

In the Southwestern United States: Arizona has 3 species of Hymenothrix, California, New Mexico and Texas each have 2 species, Nevada has 1 species and Utah has 0 species. Data approximate and subject to revision.

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.

Fruit photo above shows cypsela seed and pappi.

In Southwest Desert Flora also see: Loomis' Thimblehead, Hymenothrix loomisii and Wright's Thimblehead, Hymenothrix wrightii.

Importance to Wildlife, Birds and Livestock Trans-Pecos Thimblehead, Hymenothrix wislizeni flowers, seeds and plants may be visited, eaten and used by hummingbirds and/or small mammals including rodents in search of food, nectar, shelter and protection through cover.

Beneficial Value to Butterflies, Bees and Insects Trans-Pecos Thimblehead, Hymenothrix wislizeni has brightly colored flowers and herbaceous plants which may be visited by butterflies, moths and other insects in search of food.

Etymology: The genus “Hymenothrix” (Hymeno'thrix:) from the Greek hymen, “membrane,” and thrix, “bristle,” referring to the pappus.

The genus Hymenothrix was published by Asa Gray, (1810-1888), in 1849.

The species epithet “wislizeni” (wislizen'i:) is named in honor of Frederick Adolf Wislizenus, (1810-1889).

Ethnobotany Unknown