Plant Species of the Bright Angel Trail:
Roaring Springs prickly-poppy, Argemone arizonica

See Plant Guide to Bright Angel Trail for an introduction to this page, especially the Introduction To These Species Pages.

Argemone arizonica is not only a Grand Canyon endemic, it is endemic to the area of the North Kaibab Trail and the Bright Angel Trail. It has the most restricted distribution of any species on the Bright Angel Trail Plant Guide, with all known specimens found in an area with only a 10 miles north-south extent. The east-west extent is probably not well known due to the difficulty of surveying elevations of ~5000 feet along the Canyon; it would not be surprising if the east-west extent were considerably longer than 10 miles.


Identification status: high confidence.

McDougall says that A. munita is similar to A. arizonica but with the stems erect, the leaves lobed only about halfway to the midrib with broader lobes and prickly between the veins as well as on them.

My pictures below clearly show that the leaves are lobed nearly to the midrib, the lobes are narrow, and the leaves are prickly only on the veins. Thus all three of his distinguishing characteristics that I can measure on my pictures go to A. arizonica. (I observed decumbent stems, again consistent with A. arizonica, but they are old stems and I cannot rule out that they were erect when they were in bloom.)

Furthermore, assuming that my photographed specimens are indeed Argemone, they key to A. arizonica in the Flora of North America key as well as in the 1999 Flora of Arizona Argemone treatment. Those keys use some of the McDougall differences, plus one additional discriminant: A. munita has main lobes of leaves generally rounded at the apex, which once again does not fit the plants in my pictures; my plants have distinctly non-rounded lobes.

The descriptions of A. arizonica from all references fit my plants well for the parts that exist now in my pictures, including the capsules.

I've seen many specimens of A. munita in southern California, and they are very different looking. A. arizonica is a very striking plant just from the bluish / glaucous / silvery color of the densely-packed leaves, looking nothing like A. munita in appearance. Furthermore, I could hardly believe my eyes when I saw a specimen with a decumbent habit, strung out over 10 feet, growing in a wash (see picture below).

In 2006, I was confused about what these specimens could be since I only consulted the 1987 Grand Canyon Flora. That Flora gave only a single location for A. arizonica, on the North Kaibab Trail at 5200-5000 feet, so I didn't even consider that species as a possible determination. The 1999 Flora of Arizona treatment also only gives that location.

But after checking into it some more in 2007, it became quite clear this was the determination for these plants. Furthermore, it has been known for some time that this species occurs on the south wall of the Grand Canyon as well. McDougall 1964 says known only from the rocky slopes on the north and south walls of Grand Canyon. The Flora of North America also recognizes that it occurs on the south side of the River: Argemone arizonica grows well in Grand Canyon National Park, especially along the Kaibab and Bright Angel trails.

This discrepancy among these floras perhaps comes from the lack of vouchers from the Bright Angel Trail until 2001, when Koopman vouchered this species at mile 1.5 just above and below the first water and bathroom stop on the trail at 5820 feet elevation. I.e., McDougall may have reported it from the south side from his observations, whereas the 1987 Grand Canyon Flora and the 1999 Flora of Arizona treatment relied only on vouchers.

The determination of A. arizonica matches everything I can find out about this species except for the habitat description. These plants are growing in a flattish area of the streambed at 4208 feet, which is far from a precipitous south-facing slope!

I suspect the usual explanation for such a difference probably applies here. This species is a Grand Canyon endemic, and there are only nine vouchers of this species online, all from Roaring Springs Canyon or nearby except the Bright Angel Trail area voucher. Rare species are rarely described fully due to the paucity of vouchers, so the mismatch on the habitat doesn't bother me in the least. It is also possible that most of the plants farther upstream are growing on steep slopes, and the two specimens in the drainage are growing in atypical locations for this species, from seeds or plants that were deposited in the wash. This species is probably vouchered less often than an average species, since I wouldn't even want to touch this seriously-prickly plant, let alone try to get a voucher sample and then try to press it.

I would love to see a specimen of Argemone munita in Arizona for comparison, to make sure it resembles southern California specimens of that species and that the floral descriptions of it that differentiate it from A. arizonica are correct. Argemone munita in California is an annual; I was very surprised to learn that this species is a perennial in Arizona. It is reassuring that the illustration of A. munita in the 1999 Flora of Arizona treatment looks just like the southern California plants.

From a SEINet search on 28 September 2007, there are 9 vouchers of this species from the Coconino County portion of the Grand Canyon, including one from this trail collected on 18 Jun 2001 at mile 1.5 just above and below the first water and bathroom stop on the trail at 5820 feet elevation. Note that there may be additional vouchers at other herbaria not available through SEINet.

First occurrence on Bright Angel Trail: mile 1.46, elevation 5780 feet. The only other occurrence is just above Indian Gardens, at mile 3.69, elevation 4208 feet (1283 m).

Number of plants along Trail: Don Rideout and I observed four plants at the first location on 26 September 2021, and I observed two plants at the second location on 6 September 2007. iNat observations indicate that there are probably at least a few more plants along the Trail as of 2022.


Since iNat obscures the location of this taxon, here is a list of all iNat observations on the Bright Angel Trail that I know of as of 8 September 2022, sorted by location and then date:

Near 1.5 mile Resthouse
306/19 plant as #6
607/19 plant as #3
1405/22 plant as #15
1506/22 plants as #14
Near mile 3.69, Just before Indian Gardens

From 16 September 2006, mile 3.69 on trail:

From 6 September 2007, mile 3.69, just off-trail down the drainage:

Leaves don't get any more lobed to the base than these do:

Note that the main lobes of the leaves are narrowly-oblong in shape, with angular, not rounded, tips:

Note the presence of prickles only on the veins on the upper surface of this leaf, with even those prickles being small and sparse:

The next two pictures show the dehisced capsule fruit, which looks exactly like the illustration in A Field Guide to the Special Status Plants of Grand Canyon National Park (Brian 2000):


See Resources for Grand Canyon Flora for further information on most of these references. Entries in the second column are either the name used in that source or a page reference. The name is linked to online pages when available. If a given reference does not contain this taxon, the entry is either left blank or contains a hyphen.

Scientific NameArgemone arizonica
1987 Grand Canyon Flora NameArgemone arizonica
1987 Grand Canyon Flora page48
SEINet Image Page-
USDA PlantsArgemone arizonica
Flora of North AmericaArgemone arizonica
Jepson Manual for California treatment
Jepson Manual illustration page
Kearney and Peebles NameArgemone arizonica
Kearney and Peebles Page #1050
Vascular Plants of AZ nameArgemone arizonica
Vascular Plants of AZ volume: page30:122
Huisinga et al 2006 nameArgemone arizonica
Huisinga et al 2006 page numbers168
Epple Name-
Epple description page #-
Epple pix #-
McDougall 1964 nameArgemone arizonica
McDougall 1964 page #96
Brian 2000 NameArgemone arizonica
Phillips 1979 name-
Phillips 1979 page #-
Stockert 1967 nameArgemone sp.
Stockert 1967 page #32

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Copyright © 2007-2022 by Tom Chester.
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Last Update: 8 September 2022