Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Hymenoxys rusbyi, Rusby's Rubberweed

Scientific Name: Hymenoxys rusbyi
Common Name: Rusby's Rubberweed

Also called: Rusby’s Bitterweed

Family: Asteraceae, Sunflower Family

Synonyms: (Actinella rusbyi)

Status: Native

Duration: Perennial

Size: 1 to 3 or 4 feet (30-91-122 cm) or more; 5 feet (150 cm).

Growth Form: Forb/herb; woody; numerous branches on the upper ends of the plant; plants may be smooth or hairy, lower stems purplish-red.

Leaves: Green leaves; simple or pinnately lobed; upper leaves 3 lobed.

Flower Color: Yellow; multiple flower heads (up to 250) in flat-topped arrays; heads with both ray and disk florets; bract surrounding floral heads typically bell-shaped; fruit a cypsela.

Flowering Season: July and August to September and October

Elevation: 5,000 to 8,000 feet (1,500-2,438 m)

Habitat Preferences: Higher elevations in dry soil, open areas in pinyon juniper communities, roadsides and rocky slopes.

Recorded Range: Rare in the United States, distribution is limited to Arizona and New Mexico. In Arizona Rusby's Rubberweed is found in the northern and northwestern parts of the state and in Gila County. In New Mexico its occurrence is in the southeastern part of the state.

North America & US County Distribution Map for Hymenoxys rusbyi.

North America species range map for Rusby's Rubberweed, Hymenoxys rusbyi:
North American range map courtesy of Virginia Tech, Dept. of Forest Resources & Environmental Conservation

North America species range map for Rusby's Rubberweed, Hymenoxys rusbyi: Click image for full size map.
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 8 species and 24 accepted taxa overall for Hymenoxys. Worldwide, The Plant List includes 26 accepted species names and a further 35 scientific names of infraspecific rank for Hymenoxys.

The genus Hymenoxys was published by Alexandre Henri Gabriel de Cassinni, (1781-1832) in 1828.

In the Southwestern United States: Arizona has 12 species of genus, California has 4 species, Nevada and Texas each have 5 species, New Mexico has 10 species and Utah has 7 species. Data approximate and subject to revision.

Comments: Although rare in the United States Rusby’s Rubberweed in locally common where found above 5,000 feet (1,500 m) in Arizona. These photographs were taken of a lone specimen roadside in the Mazatzal Mountains off Highway 87 near Mount Ord, Tonto National Forest, Maricopa County, Arizona.

This species is similar to and may be mistaken for the somewhat smaller Pingue Rubberweed, Hymenoxys richardsonii which is more robust, taller and has more branches as well as a much larger distribution.

Importance to Wildlife, Birds and Livestock
Rusby's Rubberweed, Hymenoxys rusbyi flowers, seeds and plants may be visited 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
Rusby's Rubberweed, Hymenoxys rusbyi, with their brightly colored flowers and plants may be visited by butterflies, moths and other insects in search of nectar, food and shelter.

The genus “Hymenoxys” (Hymenox'ys:) from the Greek hymen, “a membrane,” and oxys, “sharp-pointed, sharp,” and apparently alluding to the pappus.

The genus Hymenoxys was published by Alexandre Henri Gabriel de Cassinni, (1781-1832) in 1828.

The species epithet rusbyi (rus'byi:) after Henry Hurd Rusby (1855-1940).


Date Profile Completed: 8/14/2012; updated 08/21/2020
Arizona Flora, Kearney, Thomas H., Peebles, Robert H., 1960, University of California Press, Berkley and Los Angeles
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database and USGS ITIS search - (accessed 08/21/2020)
The Plant List (2013). Version 1.1. Published on the Internet; (accessed 08/21/2020).
Native Plant Information Network, NPIN (2013). Published on the Internet (accessed 08/21/2020). Lady Bird Johnson Wildflower Center at The University of Texas, Austin, TX.
Gary I. Baird, FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae| Hymenoxys, 15. Hymenoxys rusbyi (A. Gray) Cockerell, Bull. Torrey Bot. Club. 31: 496. 1904. Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford.
Kleiman, Russ, Dr., Associate Botanist, Dale A. Zimmerman Herbarium; Vascular Plants of the Gila Wilderness; Hymenoxys rusbyi, (Rusby's Rubberweed); (accessed 08/21/2020). Presented in Association with the Western New Mexico University Department of Natural Sciences
Wikipedia contributors, 'Hymenoxys rusbyi', Wikipedia, The Free Encyclopedia, 9 February 2018, 16:29 UTC, [accessed 21 August 2020]
SEINet synonyms, scientific names, geographic locations, general information.
Etymology: Michael L. Charters California Plant Names: Latin and Greek Meanings and Derivations; A Dictionary of Botanical and Biographical Etymology - (accessed 08/21/2020)