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Oxytenia acerosa
Euphrosyne acerosa. Synonyms: Oxytenia acerosa, Iva acerosa. (Copperweed)
Asteraceae (Sunflower Family)

Semi-desert. Washes. Summer.
Side wash of Comb Wash, Utah, October 27, 2013.

Euphrosyne acerosa is a perennial growing in washes in three foot tall and wide massive clumps of multiple unbranched stems. Numerous elongated, branched clusters of minute flowers top each of the many stems. From a distance and at first glance one might take the plant for Stanleya pinnata, especially because of its feathery appearance, but a close-up look quickly shows the differences.

For more photographs of Euphrosyne acerosa, see SeiNet.

Euphrosyne was one of the three Greek Graces. Greek also gives us, "oxy" ("pointed") and "tenia" ("ribbon"), referring to the long, narrow, pointed leaves. The first specimen of this plant was collected for science by William Gambel in the Rockies in the early 1840s and was named and described in 1848 by Thomas Nuttall, who also named the Oxytenia genus.

Oxytenia acerosa

Euphrosyne acerosa. Synonyms: Oxytenia acerosa, Iva acerosa. (Copperweed)
Asteraceae (Sunflower Family)

Semi-desert. Washes. Summer.
Side wash of Comb Wash, Utah, October 27, 2013.

Flower heads are numerous and clustered in elongated, paniculate inflorescences (a repeatedly branched inflorescence with flowers on pedicels).

Oxytenia acerosa

Oxytenia acerosa

Euphrosyne acerosa. Synonyms: Oxytenia acerosa, Iva acerosa. (Copperweed)
Asteraceae (Sunflower Family)

Semi-desert. Washes. Summer.
Side wash of Comb Wash, Utah, October 27, 2013.

Euphrosyne acerosa flower heads have no ray flowers, just disc flowers. The outer disc flowers can develop seeds for they are pistillate (they have styles but no stamens); the inner disc flowers cannot develop seeds for they are staminate (they have stamens but no styles).

The outer pistillate flowers have no corolla; the inner staminate flowers have a narrow, yellow-white corolla.

Euphrosyne acerosa was a bit difficult for me to identify, for although the detail of the keys led me to Euphrosyne acerosa, when I read the complete descriptions of the plant I saw one major problem: there are not supposed to be pappus hairs, yet the flowers certainly seemed to have an abundance of silvery-white pappus hairs. (See the photograph at left.)

After repeating the keying process several times with several different keys and still ending up at Euphrosyne acerosa, I took another look at the flowers under the microscope and realized that the hairs are not pappus hairs at the top of the seeds, but instead are hairs that are on the body of the seeds. The plant has no pappus hairs.

Euphrosyne acerosa has another unusual characteristic: most Asteraceae have stamens with united anthers and free filaments, but Euphrosyne acerosa has stamens with free anthers and united filaments.

Two final notes about keying this plant: 1) There are disagreements among various botanical keys about the number and shape of the phyllaries of Euphrosyne acerosa. Welsh indicates that there are 5 phyllaries; Flora of the Four Corners and FNA indicate there are 10-15 in +-3 series; Intermountain says 5-7 "often 1or 2 of them shorter than and external to the others". The latter accords with my observations -- and the inner phyllaries are the same height and width.

2) When keying Oxytenia acerosa with A Utah Flora you will find that both choices in step 4 of the Asteraceae "Key 2" indicate that there are pappus hairs on all of the next species (which include Euphrosyne acerosa in step 6). If you had already figured out that the hairs of Oxytenia acerosa were not pappus hairs, you would stop at step 4 and try another direction in the key, but no other direction will lead you to Euphrosyne acerosa.

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

Oxytenia acerosa

Range map for Euphrosyne acerosa