Helianthus pauciflorus subspecies subrhomboideus. Synonym: Helianthus rigidus. (Stiff Sunflower)
Asteraceae (Sunflower Family)

Foothills, montane. Openings, woodlands. Summer, fall.
Above and left: Nature Trail, Durango West II, August 19, 2021.

This distinctive Sunflower is not common in the Four Corners area and, as the map below indicates, it does not even occur in all of Utah and Arizona.

Helianthus pauciflorus grows from 2-3 feet tall with opposite leaves well-spaced along the stiff stem. The 3 or four rows of overlapping phyllaries (showing at the top of the stem) are dark green, broad with acute tips, and mostly glabrous with fine hairs along the edges ("ciliate margins").

"Helios" is Greek for "sun" and "anthos" for "flower"; "pauciflorus" is Latin for "few-flowered"; and "subrhomboideus" is a mixture of Latin and Greek for "nearly similar to rhombic (diamond) shaped".

The Helianthus genus was named by Linnaeus in 1753 and the Helianthus pauciflorus species was named by famed botanist, Thomas Nuttall in his 1818 The Genera of North American Plants, from collections made in "Lower Louisiana", i.e., southerly sections of the Louisiana Purchase territory. I presume that Nuttall collected the new species in the St. Louis area in 1810 as he waited to join the Astor expedition of 1811. Click to read Nuttall's description.

Helianthus pauciflorus subspecies subrhomboideus. Synonym: Helianthus rigidus. (Stiff Sunflower)
Asteraceae (Sunflower Family)

Foothills, montane. Openings, woodlands. Summer, fall.
Nature Trail, Durango West II, August 19, 2021.

The photograph at left shows the interior of an unusually small, 1/3 inch wide Helianthus pauciflorus flower head.

Typical H. pauciflorus have about 70 disc flowers, but severe drought is probably the reason that this flower head (and others nearby) had only about 30. Ray flowers (shown in the above photographs), number about 10 and that too is on the low side of the typical 10-20 ray flowers.

The 7 disc flower corollas visible at left (top background) have yellow throats with red to purple lobes.

Arising from the receptacle (bottom of photograph) and almost as tall as each disc flower, are very thin, green-white scales, typical of the chaff of all species of Helianthus. Two separate scales almost form a tube around each disc flower.

From the top of each cypsela (seed) and therefore just below the corolla, are the pappus appendages. Visible here is just one pappi scale (leaning outward at the middle far left of the photograph). All floras indicate that each H. pauciflorus flower has 2 pappus scales almost as long as the corolla and often have an additional 1-4 scales less than half that size. The scales are said to fall off very early and readily and that probably accounts for the fact that I observed only one short scale in place.

Helianthus pauciflorus subspecies subrhomboideus. Synonym: Helianthus rigidus. (Stiff Sunflower)
Asteraceae (Sunflower Family)

Foothills, montane. Openings, woodlands. Summer, fall.
Nature Trail, Durango West II, August 19, 2021.

Leaves are almost always opposite, reduced in size upward, short petiolate or sessile, and have blades ranging from lanceolate to compressed diamond shaped, i.e., sub-rhombic.

Stems are usually single and glabrous near the top with short, stiff hairs elsewhere.

The leaf upper surface and edges have stiff, minute, slightly curled hairs which give them a sandpaper feel. The lower surface may have hairs similar to those on the upper surface, may also be gland dotted, or may be glabrous.

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 Helianthus pauciflorus subspecies subrhomboideus