Southwest Colorado Wildflowers, Stenotus armerioides

Stenotus armerioides

Stenotus armerioides. Synonym: Haplopappus armerioides. (Goldenweed, Ring Grass Sunflower)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Openings, woodlands. Late spring, early summer.
Arches National Park, Utah, May 4, 2005 and
Canyons of the Ancients National Monument, November 19, 2019.

This is a very common and lovely plant of dry open lowlands. It is often found in sand and gravel soils, commonly on rim rock, and commonly in Pinyon/Juniper forests. Its circular growth pattern; bright green, thin, vertical leaves; dried old leaves; and abundant, bright yellow flowers help identify it. As plants age, they grow outward in a ring, slowly expanding the ring over the years. It is common for the inner part of the ring to have died and then woody roots and stems are exposed. I have seen plants six feet in diameter and these must be many decades old.

Thomas Nuttall collected the first specimen of this plant for science along the headwaters of the Platte River on his trip to the Pacific with the Wyeth Expedition of 1834-1837. He named the plant Stenotus armerioides. Asa Gray renamed it Aplopappus armerioides in 1884, Kuntze renamed it Aster armerioides in 1891, and Welsh renamed it Haplopappus armerioides in 1983.

"Stenos" is Greek for "narrow", referring to the leaves. "Armerioides" is Latin for "similar to Armeria", probably a genus of Dianthus flowers.

The common name, "Ring Grass Sunflower" (or just, "Ring Grass") is what Betty and I call this plant -- for pretty obvious reasons: grass-like leaves in a ring. You will find a number of other common names for this plant -- and most other plants. There is no standardization for common names; they vary from person to person, place to place.

Stenotus armerioides

Stenotus armerioides. Synonym: Haplopappus armerioides. (Goldenweed, Ring Grass Sunflower)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Openings, woodlands. Late spring, early summer.
Above: Lower Cross Canyon, Utah, May 8, 2019; Arches National Park, October 23, 2017.
Left: Canyon of the Ancients National Monument, April 21, 2016 and April 25, 2007.

In the Four Corners area, Stenotus armerioides is often the dominant wildflower species in the gravels of canyon rims from 5,000-7,500 feet.

In several of the photographs, especially in the photograph immediately above, you can see the dead tufts of leaves at the base of the green leaves. Because of these dead leaves and the relatively similar green leaves, Stenotus armerioides is often difficult to distinguish from Petradoria pumila. The above photograph also shows the dried flower stems and the relatively large dried phyllaries that surrounded the base of the flower head. The flowers of Petradoria pumila are in much smaller clusters than those of Stenotus armerioides and therefore you will find clusters of much smaller dried phyllaries for Petradoria than for Stenotus.

It is common to find the exposed roots of dead Stenotus armerioides plants.

Leaves are a distinctive bright green, mostly in a thick basal rosette.

Stenotus armerioides

Stenotus armerioides. Synonym: Haplopappus armerioides. (Goldenweed, Ring Grass Sunflower)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Openings, woodlands. Late spring, early summer.
McElmo Canyon, Canyon of the Ancients National Monument, April 27, 2005.

This young Stenotus armerioides is about 18 inches in diameter and already shows the typical ring growth with a dead center.

Stenotus armerioides

Stenotus armerioides. Synonym: Haplopappus armerioides. (Goldenweed, Ring Grass Sunflower)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Openings, woodlands. Late spring, early summer.
McElmo Canyon, Canyon of the Ancients National Monument, April 27, 2005 and April 18, 2010.

Flowers are very showy golden and buds are glabrous waxy with prominent dark green tips on the phyllaries.

Stenotus armerioides

Stenotus armerioides. Synonym: Haplopappus armerioides. (Goldenweed, Ring Grass Sunflower)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Openings, woodlands. Late spring, early summer.
Lower Cross Canyon, Utah, April 24, 2019.

This magnificent plant has over 150 buds.

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 Stenotus armerioides