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Orobanche arizonica  (Arizona Broomrape)
Orobanchaceae (Broomrape Family)

Semi-desert.  Woodlands, meadows.  Spring, summer.
Near Corona/Bow Tie Arches Trail, Utah, June 7, 2007.

Originally my opening paragraph for this page read as follows:

The plant pictured at left is certainly an Orobanche, but I am less certain of its specific epithet.  The keys for A Utah Flora and Intermountain Flora indicate the plant shown at left is O. ludoviciana variety cooperi.  The more up-to-date Synthesis indicates that this name is a synonym for O. cooperi (or O. cooperi variety cooperi).  This species may also include what is often named O. multiflora.  It is all a bit perplexing.  As Stanley Welsh (the author of A Utah Flora) indicates in trying to separate varieties of O. ludoviciana, "none of the diagnostic criteria seem to hold...."

In March of 2013, Turner Collins, Orobanche expert and Evangel University Professor Emeritus, emailed me the following:

I am working on the genus Orobanche for the Flora of North America Project, and was surveying online photos of Orobanche cooperi when I came across the photos on your website. The plant shown has been considered a small flowered form of O. cooperi for some time.  I ascribed to this same identification until I began reviewing the genus for the Flora.  This plant is an undescribed species that is found only in the high deserts of the intermountain region and the Mogollon plateau in Arizona.  It seems to be host specific on Gutierrezia, whereas the true O. cooperi parasitizes a number of Sonoran Desert shrubs, members of Asteraceae.  The flowering period is June-July whereas, O. cooperi is finished by early May at the latest.  The dimensions of the various floral parts is generally smaller than all of the subspecies of O. cooperi.

It is not to be confused with O. multiflora or O. corymbosa, both of which occur in the area.  Both these species have larger flowers with distinctly rounded corolla lobes and generally utilize different hosts.

Collins and Yatskievych published the new species description in 2015 in the on-line botanical web site, Phytoneuron. Click to read the description and an in depth discussion of the Orobanche genus.

The description has this to say about the relationship of O. cooperi and O. arizonica:

During the process of reassessing the taxonomic status of Orobanche cooperi, a set of specimens accumulated that were morphologically and ecologically distinct from the plants now determined as that species. They represent populations of a smaller-flowered Orobanche with acute corolla lobes found mostly north of the Mogollon Rim and widely distributed in the four corners region of Arizona, New Mexico, Utah, and Colorado.... Previously, these specimens have been identified as either O. cooperi or O. ludoviciana or sometimes as O. multiflora. Three factors initially brought our attention to these plants. They flower in the summer, whereas O. cooperi flowers from late winter to late spring. They occur at higher elevations and latitude than populations of O. cooperi from the Sonoran Desert. Finally, they utilize Gutierrezia as primary hosts, as contrasted with O. cooperi, which utilizes mostly Ambrosia. The habitat for these plants is either pinyon-juniper woodland or cold desert-shrub associations of the Colorado Plateau and contiguous areas.

Thomas H. Kearney is credited with the collection of the type specimen for O. arizonica: "Marsh near Tuba City", Arizona at 5,050', September, 1935. At the time of that collection the plant was identified as O. cooperi.

Orobanche arizonica  (Arizona Broomrape)
Orobanchaceae (Broomrape Family)

Semi-desert.  Woodlands, meadows.  Spring, summer.
Near Corona/Bow Tie Arches Trail, Utah, June 7, 2007.
Cannonball Mesa, June 12, 2007.

Orobanchaceae are uncommon in some areas but unmistakable when you do find them.  And when you do find one, be sure to look around for more.  They tend to be quite common in selected areas.  Orobanchaceae lack chlorophyll and have large roots which surround host roots and gain nourishment from them; they are thus "parasitic".  (Click to see the roots of another Orobanchaceae, Orobanche fasciculatum).   Each species of Orobanche is usually parasitic on roots of just certain plants; O. arizonica is apparently parasitic on Gutierrezia and the plant shown at left was most likely parasitizing the nearby Gutierrezia sarothrae. 

The genus name, Orobanche, is derived from the Greek "orobos" ("vetch") and "anchein" ("to strangle") referring to the habit of some Orobanche of being parasitic on legumes (a number of legumes are commonly called "Vetch").

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

 

Click for a range map for Orobanche arizonica.

 

Range map for Orobanche cooperi