Possible subspecies of Penstemon palmieri

There is a population of Palmer’s penstemon in Grand Canyon Park that are about half the size they are supposed to be according to almost all the field guides and web sites. I have verified that they are Penstemon palmieri. I have observed them on the rim near Hopi Point, and along the South Kaibab trail above about 6000 feet elevation. There is no individual taller than about 30 inches. By contrast, there is a population I am familiar with 100 miles to the south, on the ridge between Mingus Mountain and Woodchute Mountain, where most of the individuals are between 3 and 5 feet, which fits the field guides’ descriptions.

The Forest and Mountain Plants of Northern AZ field guide says there are 2 varieties of Penstemon palmieri, but gives no indication of a difference in height. The USDA website https://plants.usda.gov/plantguide/pdf/pg_pepa8.pdf says that according to an old book there are 3 varieties, but also gives no information:
Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L. Reveal, & P.K. Holmgren 1984. Intermountain Flora. Volume Four. Subclass Asteridae (except Asteraceae). The New York Botanical Garden, Bronx, New York.

The cheapest copies of Intermountain Flora volume 4 I can find go for $85. Can someone who has access to this book look up the information and post an image to this topic? I am not a naturalist, but it seems to me that a population that is uniformly smaller than another geographically isolated population perhaps should be considered a subspecies. Perhaps the accepted meaning of “variety” and “subspecies” has changed since Intermountain Flora was published.

I don’t know the extent of this population of small Penstemon palmieri. It seems that information on the “varieties” of Penstemon palmieri has been lost over time. It could be a research project for someone.


I was curious so I tried a little search. This is a difficult Google. The best description of the differences I found was here: https://wolfelab.wordpress.com/2014/06/04/penstemon-of-the-day-penstemon-palmeri/

I didn’t find anything about the height though.

The Biodiversity Heritage Library can be a good place to look for this kind of thing.

This entry in Flowering Plants and Ferns of Arizona might be helpful:

There’s a protected variety described here:

Here’s the key from IMF vol 4, same as the Lodewick Penstemon key.

1 - Corolla tube (the small cylindrical part at the base of the corolla) 4-6 mm long, upper leaves always connate.
2 - Peduncles, pedicels, and calyces glandular… var. palmeri (e & s NV, e & se CA, NW & central AZ)
2’ - Peduncles, pedicels, and calyces not glandular … var. eglandulosus (Cedar City to Zion and Kaibab Plateau)
1’ - Corolla tube 7-8 mm long, upper leaves connate or not … var. macaranthus (rare in central NV)

Since preserved specimens are usually required to name a new taxon and permits are required to collect in national park units (https://www.nps.gov/grca/learn/nature/research_permits.htm) you may need to enlist the help of staff from the park museum (https://www.nps.gov/grca/learn/historyculture/muscol.htm) or a nearby herbarium such as the Museum of Northern Arizona Herbarium or the Desert Botanical Gardens.

I hope that helps!

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I found a few other references that might be helpful. Along with Intermountain Flora, these agree that Penstemon palmieri is from 50 cm to 140 (or 200) cm tall, but none mention any difference in height between varieties.


I’m curious when IMF volume 4 was originally published. The copies available for sale on the web say 1984, but from the images I suspect it was originally published much earlier than that.

It was published in 1984. The earliest volume (1) was published in 1973 and they kept the same general design through the last volume (7) in 2017.

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