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Rhinotropis subspinosa

Rhinotropis subspinosa

Polygala subspinosa

Polygala subspinosa

Rhinotropis subspinosa

Rhinotropis subspinosa. Synonym: Polygala subspinosa. (Milkwort)
Polygalaceae (Milkwort Family)

Semi-desert.  Rocky, sandy slopes.  Spring.
Lower Cross Canyon, Utah, May 17, 2017 and Canyons of the Ancients National Monument, May 11, 2011.

Polygala subspinosa

Polygala subspinosa

Rhinotropis subspinosa. Synonym: Polygala subspinosa. (Milkwort)
Polygalaceae (Milkwort Family)

Semi-desert.  Rocky, sandy openings.  Spring.
Canyons of the Ancients National Monument, April 27, 2007 and April 18, 2010.

Rhinotropis subspinosa is rare in a few western counties of Colorado and occurs in only one northwestern county of New Mexico; it is more common and widespread in Utah, and it is found across the northern tier of Arizona counties.  (See the map below.)

Rhinotropis subspinosa typically grows about five inches tall and wide in an open, rounded form but can be up to ten inches tall and wide.  Woody stems persist and become spiny.  Bright green leaves grow quickly in early spring.  Rhinotropis subspinosa grows at elevations from about 4,000 to 7,000 feet in dry, open areas. 

In 1753 Linnaeus named the genus Polygala, Greek for "much milk", but the name was applied to some now unknown plant reputed to increase milk production in cattle.  Polygala subspinosa was named by Sereno Watson in 1873 from a specimen collected by an unknown botanist in 1862.

In 2011 J. R. Abbott published "Notes on the Disintegration of Polygala, With Four New Genera for the Flora of North America". His work re-evaluated the genus Polygala and gave the species shown on this page its new genus, Rhinotropis (from the Greek "rhino" meaning "nose", because of the nose-like, yellow projection of the flower keel. The Greek "tropis" means "keel").

"Subspinosa" means "almost spiny".

Rhinotropis subspinosa

Rhinotropis subspinosa

Rhinotropis subspinosa

Rhinotropis subspinosa. Synonym: Polygala subspinosa. (Milkwort)
Polygalaceae (Milkwort Family)

Semi-desert.  Rocky, sandy openings.  Spring.
Canyons of the Ancients National Monument, May 11, 2011 and April 21, 2016.

Flowers have characteristics that remind one of plants in Fabaceae (Pea Family) and Fumariaceae (Fumitory Family).  Whatever they remind us of, they are certainly beautifully exotic.  Weber says, "An amazing flower indeed" and Welsh says, "The brightly colored flowers, sometimes produced profusely in this clump-forming plant, are truly attractive.  It should be considered for horticultural use".

Flowers are from 8-13 cm long with 5 sepals, two of which are enlarged petal-like wings which surround the three petals, two of which are reflexed at their tip and darker purple and one of which is keel-like and yellow and is terminated with a pouch-like prominently rounded tip.

Rhinotropis subspinosa

Rhinotropis subspinosa. Synonym: Polygala subspinosa. (Milkwort)
Polygalaceae (Milkwort Family)

Semi-desert.  Rocky, sandy openings.  Spring.
Lower Cross Canyon, Utah, May 17, 2017.

Flower buds, fresh flowers, fading flowers, and dangling brown seed capsules appear on the same plant.

The thorny twig tips are actually not as menacing as the white thorny tips shown above because they are new soft growth. Rhinotropis subspinosa stems commonly (always?) die back nearly or part way to the ground each year. Some spiny stems persist, dry, and become the white skeletons you see in photographs above.

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

Polygala subspinosa

Range map for Rhinotropis subspinosa