Hymenoxys richardsonii var. floribunda. Synonym: Picradenia richardsonii. (Colorado Rubberplant)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Meadows, openings, woodlands, shrublands. Spring, summer, fall.
Above: Northeast Arizona Navajo Reservation, June 3, 2006 and Durango West Nature Area, August 24, 2021.
Left: Northeast Arizona Navajo Reservation, June 3, 2006.

Hymenoxys richardsonii can grow with just single stems, but as the photograph above shows, it can (and more commonly does) also grow with many stems. Basal and stem leaves are narrow and basal leaves grow in tufts. All leaves may range from glabrous to slightly hairy and may be entire or in 3-7 very narrow divisions.

The vertical, yellow projections around the edge of the flowerheads shown at left will grow into the rays shown on the flowerhead near the upper right of the first photograph at left.

Below the flower heads, as shown especially in the second photograph at left, are hairy phyllaries (bracts). Two sets of phyllaries overlap each other. The outer phyllaries are joined from their base upward for about half of their length. I have outlined in red the upper separated parts of two adjacent phyllaries.

In the upper right corner of the second photograph at left you can see that the outer phyllaries are not consistently green. The edges look papery-tan ("chartaceous"), and you can also see that the phyllaries bulge; they are not flat.

In 1833 Joseph Hooker described this species and named it Picradenia richardsonii in honor of explorer and naturalist John Richardson who discovered the species in Saskatchewan, probably on his 1825-1826 North American expedition. The plant was placed in the Hymenoxys genus by Cockerell in 1904. Click for more biographical information about Richardson.

The genus name, "Hymenoxys", is from the Greek for "membrane" and "sharp", alluding to the sharp pappus scales.Alexandre Cassini, naturalist and Asteraceae aficionado, named the Hymenoxys genus in 1828.

Roots of Colorado Rubberplant have latex and early in the 20th century the plant was looked at as a source for rubber.  

Hymenoxys richardsonii var. floribunda. Synonym: Picradenia richardsonii. (Colorado Rubberplant)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Meadows, openings, woodlands, shrublands. Spring, summer, fall.
Northeast Arizona Navajo Reservation, June 3, 2006 and Durango West Nature Area, August 24, 2021.

In the top photograph at left, tufts of leaves are close to each other as this plant is quite healthy and has sent out branches from one tuft (actually from the "caudex" at the base of a tuft) to start another tuft. Some leaves are deeply divided but most are entire, whereas in the second photograph most leaves are deeply cut, i.e., they are pinnately divided into three to seven segments.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Hymenoxys richardsonii