Rising as a solid wall of mountains above the Great Plains from Las Vegas, New Mexico to southern Wyoming, the Colorado and New Mexico Rockies are some of the most iconic mountains of western North America. Historically referred to as the Crown of the Continent, the Colorado portion is home to most of the highest peaks in the lower 48 states, with over 50 mountains rising above 14,000 ft (4,300 m). The variety of substrates in the alpine, a wide precipitation gradient ranging from 17 - 80 inches (43 - 203 cm) annually, and a heterogeneous landscape have created diverse niches for many endemic plants.

Thirty-five alpine species are endemic to Colorado alone, one of the highest numbers of alpine endemic plants in North America. An additional 10-20 species are endemic to the Southern Rockies with a range centered within the Colorado Rockies. Finally, several species are endemic in the political borders of New Mexico, Arizona, and Utah but fall either on the border or beyond the Southern Rockies Ecoregion and are outside the scope of this article.

This article explores Southern Rockies endemics that I have sought out, serendipitously stumbled upon, or cultivated during my career at Denver Botanic Gardens.

Charismatic Columbine, Penstemon, Buckwheat, and Paintbrush

It’s not surprising that some of the genera most associated with the West have endemic alpine members centered in Colorado.

Aquilegia laramiensis Although not a true alpine, I will begin this list with A. laramiensis since it fits in a rock garden nicely. Endemic to the Laramie Mountains of Wyoming, which technically do not reach alpine as the peaks top out at 10,000 feet (3,000 m), this little columbine is found on the summit of Laramie Peak, the highest peak in its native range. It has proven amenable to cultivation and enjoys cool and partially sunny sites in Colorado landscapes with regular watering. Like many columbines, A. laramiensis hybridizes in the garden, especially after several generations. It is listed as both a National Forest and Bureau of Land Management (BLM) sensitive species.

Aquilegia saximontana is one of Colorado’s most charming alpine plants, found from 9,000 to 13,500 feet (2,740 – 4,000 m) with populations concentrated at the tree line. Easily amenable to cultivation, it has been speculated that there might be more plants in cultivation than in the wild where seed predation from mammals severely diminishes seed set. Cultural conditions are similar to A. laramiensis. Note that A. flabellata var. pumila and even hybrids of A. bertolonii and A. pyrenaica often masquerade in cultivation as A. saximontana, which is differentiated by its small pendulous flowers.

Castilleja haydenii: With bright pink or magenta flowers, this plant catches one’s attention in its native range of southern Colorado and northern New Mexico. I have tried growing it with no long-term success even in my high elevation garden in north Routt County. It would be a most welcome addition to a rock garden.

Castilleja puberula is less show-stopping due to its pale-yellow color, but this species is very interesting viewed from up close due to the lovely dissected hairy bracts. This specialty of the Front Range has scattered locations across southwestern Colorado and some potential populations in Idaho and Montana. It is tracked as a threatened species in Colorado and to my knowledge it has not been cultivated intentionally. It does grow in the constructed rock gardens around the visitor center at Mount Goliath, which is one of the most accessible places to observe it.

Eriogonum arcuatum var. xanthum occurs sporadically across the high peaks of Colorado and up into the Park Range of Routt and Jackson counties. This is one of the loveliest eriogonums for rock gardens. It has been cultivated several times, never persisting as long as one would like.

Eriogonum coloradense is found from the steppe up into the alpine, like several of our regional endemics. I have only observed the steppe populations in the Gunnison Basin. Although difficult to source, it has proven to be a very adaptable garden plant in my high elevation garden, and it grew splendidly at Denver Botanic Gardens but was not as long-lived.

Penstemon hallii: The specific epithet commemorates Elihu Hall, an early botanist in Colorado. Its range is centered in southern and central Colorado with some outlying populations in north-central Colorado. Large blue or violet flowers on a compact plant make this one of the best alpine penstemons for troughs. Easy in cultivation, it can be long-lived for a penstemon.

Penstemon harbourii is another obligate high elevation dweller; this species is found in scree and frequents some of Colorado’s high peaks in the central and southern part of the state. It resembles a blob of blue-violet flowers in its desolate rocky environment. It has proven much more difficult than P. hallii in cultivation. Jared Harbour, who this species commemorates, was Elihu Hall’s cousin

Penstemon uintahensis is a species that is not found in the political boundaries of Colorado but is endemic to its namesake mountains just across the Utah and Colorado border. Found in spruce-fir forests and up into alpine elevations, this species superficially resembles P. hallii and is amenable to cultivation but has acted more like a biennial or very short-lived perennial in Denver and Steamboat Springs. As a note, the Uintah and Wasatch ranges are part of the Middle Rockies, but floristically are a fascinating mix of Southern Rockies flora with northern elements. Utah has a few other unique alpines, but they do not reach Colorado.

North American Endemic Genera with Endemic Species in the Southern Rockies

It is perhaps not surprising, given the somewhat isolated nature of North and South America both geologically and historically, that some genera are only found in North America. Penstemon, Cymopterus, Besseya (syn. Veronica), Dieteria, Heuchera, Telesonix, Townsendia, and Xanthesmia are all genera endemic to North America that also have alpine members. Three genera starting with “T” (Telesonix, Tonestus, and Townsendia) are endemic to the American West.

Besseya alpina (syn. Veronica besseya) is both growable and delightful to encounter in the wild. It is one of the first alpine plants to bloom each year. The purple-blue fuzzy spikes mean that winter’s grip has come to an end in the highest parts of the Rockies. This species has done best in troughs in Denver, Steamboat Springs, and northern Routt County. This species is shy to bloom in cultivation, it seems.

Besseya ritteriana (syn. Veronica ritteriana) is far less showy than B. alpina, but its greenish-white spikes are a true plant nerd’s dream. This species is centered on the high San Juans of southern and southwestern Colorado, another small area that contains endemic alpine plants. The San Juans are a young mountain range compared to the rest of the Colorado Rockies and are comprised of both sedimentary rocks and widespread volcanic substrates. The endemic flora exploits both the limestone and volcanic areas.

Cymopterus alpinus (syn.  Oreoxis alpina): This diminutive parsley relative represents an interesting branch of the Apiaceae, a family with a large representation in the Southern Rockies. C. alpina is quite common across the alpine tundra in Colorado, but it’s often overlooked because of its small size and less charismatic flowers. The flower comes in yellow but paler individuals do exist. It is growable in a trough or crevice garden.

Cymopterus bakeri (syn. Oreoxis bakeri) is listed by Ackerfield as being endemic to Colorado, but Flora of Utah also claims the species and I have seen something identified as this species in the Cedar Breaks of Utah. There is a sticky mess in the field and herbarium as to which is the true plant.

Cymopterus humilis (syn. Oreoxis humilis) is endemic to Pikes Peak and currently is the only true endemic species on this isolated high mountain. This species has been cultivated for at least brief periods in several of my gardens.

Dieteria pattersonii ( syn. Machaeranthera pattersonii, Aster pattersonii) is currently subsumed under Dieteria bigelovii, a low to moderate elevation species that is tall and biennial. Dieteria pattersonii, however, is a multi-stemmed perennial restricted to central Colorado and possibly northern New Mexico. I have only seen the New Mexico material in herbarium specimens, and it may, in fact, be a different taxon.

Heuchera bracteata, one of two Colorado endemic coral bells, has a sophisticated charm. H. bracteata has bright green to yellowish-green flowers which I find very attractive and refreshing in the late spring to summer amidst a rush of other brightly colored wildflowers. A true saxatile plant, it is always found on rocks. In Denver, it is easy to cultivate in the garden in shade and with some regular watering.

Heuchera hallii sports creamy white flowers in looser spikes than H. bracteata. This species is endemic to the greater Pikes Peak region often found within the Pikes Peak granite batholith. I have seen it only once in the wild but have grown it since I was a kid. Long-lived and durable, I would never be without it.

Tonestus pygmaeus: The American West is covered by yellow composites and many superficially resemble one another (unless one teases them apart, sometimes literally). This species forms compact mounds and pseudo-cushions in the most exposed locations, which are covered with bright yellow flowers in high summer. It has been cultivated but is never very long-lived.

Telesonix jamesii: I would vote for this as one of Colorado’s most charismatic alpines. After Aquilegia and Eritrichium have been sought out, photographed, and checked off the list, this plant comes to mind as one of Colorado’s must-see alpines. Plants with bright magenta flowers growing up vertical cracks on Pikes Peak is a special sight. This genus has another species endemic to the north which grows on limestone, but it does not reach Colorado.

Townsendia rothrockii: Along with T. leptotes, this is one of our true alpine Easter daisies. A few other species reach the subalpine, but only these two make it above treeline. This species is very growable and is one I propagate from seed each year as it is short-lived and has not self-sown at Denver Botanic Gardens.

Xanthismia coloradoensis: Along with the Townsendia, Xanthismia strives to make sure that not all composites are DYCs (Damn Yellow Composites). Like many asters, this species has had a bit of an identity crisis as of late, with some taxonomists placing it in the genera Machaeranthera or Aster, but hopefully the nomenclature is settling. With bright pink and pale pink flowers, it does well in a trough or rock garden where its presence, while often brief, is always welcome.

Genera Endemic to North and South America with Alpine Species Endemic to the Southern Rockies

North and South America were not connected until about three million years ago. Since then, plants and animals unique to each continent have migrated to the other. Hymenoxys, Ipomopsis, and Eriogonum represent genera that are native only to North and South America, with a concentration in the western and central U.S. and in the Andes and Patagonia.

Hymenoxys brandegeei is related to one of the most photogenic alpines of the Rockies, old man-of-the-mountain (Hymenoxys grandiflora). Hymenoxys brandegeei has smaller flowers but offsets size by being perennial as opposed to monocarpic. Both species have been cultivated at Denver Botanic Gardens with surprising ease. With H. brandegeei one does not have to keep a constant stream of seedlings coming since it is not monocarpic.

Ipomopsis globularis is a member of a genus that does red so well. It is good to know other species within this genus that do white to icy blue just as well. This species is restricted to the central part of the state, with outliers in Idaho, but sometimes those are considered to be something else. Growable in the garden it tends to be biennial, monocarpic, or a short-lived perennial. It is fragrant to some, but others find the scent offensive. It is found in central Colorado on the Mosquito Range and Hoosier Pass.

Cirsium

Recent genetic work on the high elevation thistles of Colorado and neighboring states by Dr. Jennifer Ackerfield, Head Curator of Natural History Collections and Associate Director of Research at Denver Botanic Gardens and the author of The Flora of Colorado, has resulted in newly described species and refined distributions of known species. I am highlighting these newly described and resurrected taxa to clarify the confusion previously surrounding this genus (Personal communication with Jennifer Ackerfield, Jan. 4, 2022). Dr. Ackerfield will be publishing more on this work in the future and also updating her findings in the next edition of The Flora of Colorado.

Cirsium funkiae is one of the most enigmatic of Colorado’s high alpine flora. I almost consider C. funkiae akin to an alpine dragon in plant form. Found in screes and rockslides it so far has proven ungrowable at both Denver Botanic Gardens and in my high elevation garden. It is often monocarpic, like so many large alpine plants.

Cirsium scopulorum was included in C. funkiae until Jennifer Ackerfield’s work demonstrated it was a unique taxon. Found further north in Colorado, it has pinkish flowers and, like C. funkiae, has proven difficult to cultivate long-term, only living for a year or two and never flowering. Cirsium culebraensis, C. hesperium, and C. griseum var. osterhoutii are also endemic to high elevations of Colorado and Ackerfield’s research has clarified the relationship between these taxa.

The Best of the Rest of the Endemics

The following genera have no specific geographic distribution, but rather tend to have members scattered across the temperate regions of the Northern Hemisphere and many are even found in temperate or high elevation areas of the Southern Hemisphere. However, within these genera are taxa that are specific to certain regions or substrates.

Astragalus molybdenus, the Leadville milkvetch, is one I have only seen in the wild, limited to the Leadville limestone and similar substrates. It represents a group of alpines that are endemic to a few limestone areas of the central Colorado Rockies.

Aster alpinus var. vierhapperi is a disjunct rather than strict endemic, but it’s rare in Colorado and has a fascinating distribution stretching from the Altai in Asia across to Alaska and down through the Canadian Rockies and into Colorado. Outside of Canada and Alaska, it may be most plentiful in Colorado. The distribution pattern stretching from central Asia, jumping the Bering Strait, and hopping down the Canadian Rockies and into the highest peaks of the Rockies is a pattern shared by some of Colorado’s rarest alpines, but that is a story for another time.

It is perhaps not surprising that there are no endemic alpine Carex in Colorado. In terms of total numbers of species, Carex is the largest genus in the Colorado alpine. Those found in the alpine tend to be generalists inhabiting moist habitats or are found in specific high elevation habitats throughout the U.S. Rockies. A quick scan of BONAP (Biota of North America Program) range maps reveals the following species are worth noting. Carex arapahoensis is found in Wyoming, Colorado, and southeast Utah. Carex ebenea and C. elynoides are found in the Rockies from southern Montana to New Mexico and Arizona. Carex nelsonii is found in Montana, Wyoming, Colorado, New Mexico, and Utah. It is only common in Utah and Colorado according to BONAP. Carex nova is endemic to the Southern and Middle Rockies across six western states. Carex perglobosa is about as close to endemic in the Southern Rockies as one can find in a high elevation sedge found between 11,000 and 13,000 feet. It is listed as common in Colorado and two counties in Utah according to BONAP.

Delphinium alpestre: The Himalayas have their exquisite delphiniums, and so do the Southern Rockies. Found from New Mexico into Colorado, this scree-dwelling, cobalt-blue delphinium is growable, at least for short periods. It is one of Colorado’s most beautiful but rarely seen alpines.

With six species endemic, the drabas win for having the most Colorado endemic alpine species in a genus. As they are a bit difficult to differentiate (true taxonomic identification relies on hair shapes and patterns on the leaves and stems), I have undoubtedly seen more than I realize.

Draba exunguiculata: I have seen this species along with D. grayana but I do not have photos to prove it.

Draba graminea is an adorable little plant endemic to the San Juans. My fingers in the photo give the scale on the individuals we found during the 2021 NARGS conference in Durango. It can make larger mats than the photo shows.

Draba smithii is the only white-flowered draba that is endemic to Colorado; it has relatively large flowers, nice grayish leaves and has been grown at both Denver Botanic Gardens and my home garden in a trough. Sadly, it did not persist and sets little seed.

Erigeron pinnatisectus: While not endemic to Colorado, its range is centered squarely in Colorado, extending into the Snowy Range of Wyoming and down into northern New Mexico. It is a superb Erigeron for the trough or rock garden. Sadly, it, like our Aquilegia saximontana, suffers identify fraud in cultivation, with forms of Erigeron compositus masquerading as it. It has pinnate leaves while E. compositus has a more palmate-shaped leaf.

Paronychia pulvinata, one of our greatest cushion-forming plants, is endemic in the Southern Rockies. It jumps over into the Uintahs, which are technically part of the Middle Rockies in terms of ecoregions but are spatially closer to the Southern Rockies than the Wind Rivers, Tetons, and Bighorns of Wyoming where it is absent.

Physaria alpina: The Brassicaceae, or mustard family, is high up there for numbers of endemic plants in cold, high places. Physaria alpina is one of the most attractive members of a genuinely attractive genus. Bright yellow to almost orange flowers surround a silvery rosette of leaves. It has been cultivated in Denver, Vail, and Steamboat Springs. The genus is found in North America, South America, and far eastern Asia.

Podistera eastwoodiae commemorates Alice Eastwood, a keen botanist working in Colorado at the end of the 19th century. My love of parsleys shows through again. One of the most overlooked plants superficially resembling the Cymopterus (syn. Oreoxis), it has wider leaves and larger flowers. I have only seen it once or twice in all of my jaunts. To my knowledge, it has not been cultivated. The genus is centered in the American West but, like several genera, a few taxa in Podistera skip across the Bering Strait into eastern Asia, most likely due to the land bridge that has formed several times in geologic history.

Polemonium confertum, Colorado’s only endemic Polemonium, is even more stunning than the more widely spread and beautiful P. viscosum. It has larger heads of flowers and inhabits screes and rocky areas, while P. viscosum prefers stable tundra. Seed has geminated easily, and we will see how it does as a garden plant.

Primula angustifolia: Highly photogenic, a photo of John Fielder’s still burns bright in my mind from childhood of the fairy primrose with Eritrichium argenteum, Trifolium nanum, and Claytonia megarhiza. This Primula is distributed squarely in Colorado only leaving the state to follow the Sangre de Cristo Range into New Mexico. The holy trinity of Eritrichium, Trifolium, and Claytonia can be found up into Montana, sometimes still cohabitating.

Ranunculus macauleyi: Most high mountain ranges have their buttercups. Botanists slice and dice them into various genera periodically but in the end, the gestalt is the same: waxy, shiny yellow, white, or pale pink flowers. This species is centered in Colorado and northern New Mexico in the San Juans and a bit beyond. Fuzzy black hairs on the reverse of the flowers set this species apart from Colorado’s other two large yellow-flowered alpine buttercups. Ranunculus macauleyi tends to hang out around melting snowbanks and would be as tricky as Ranunculus adoneus in cultivation.

Senecio soldanella: I must admit I have a thing for yellow composites as well as parsleys. While there is a seemingly endless array of DYCs in the Rockies, very few are endemic to alpine elevations of the Southern Rockies. This exquisite dweller of screes has large purplish leaves and bright yellow sun-shaped flowers.  It has been cultivated by a handful of the most devoted, but rarely for long.

Senecio taraxacoides: Another high elevation scree dweller, do not let the specific epithet turn you off. It is super cute and super challenging to cultivate. Senecio taraxacoides cohabitates with Penstemon harbourii and Senecio soldanella on some of our highest and most scenic screes.

Packera porteri: Packera and Senecio were once lumped together, but now the Packera have their own genus.  This is another high elevation scree dweller from the Elk Mountains of Gunnison County and down into the San Juans. I have seen it only once near Crested Butte. It is lovely, like all scree plants. I doubt more than a few people, if any, have tried to tame it in cultivation.

Eutrema penlandii: The genus Eutrema is found from Mexico across the high latitudes of North America and Eurasia. Colorado has one endemic species that is specific to high elevation fens. Cold, wet, and alkaline is what it wants. Seed germinates and plants have been grown on at DBG but, to my knowledge, we have never gotten it to flower in cultivation. The entire plant is not much larger than my fingernail. One can find it in it habitat by accompanying the botanists who monitor it or perhaps you could be looking down while momentarily pausing in its sedge-rich environment.

Clovers that Excite

Johan Nilson of Göteborg Botanic Gardens, after touring through Colorado alpine areas, considered our clovers some of our most interesting plants. I would agree with him.

Trifolium attenuatum, the paler pink of the two endemic clovers, is centered in southern Colorado. You will find it on the Spanish Peaks, the Sangre de Cristos, and in the San Juans. It has proven to be growable in my Steamboat garden.

Trifolium brandegeei: Deep pink, almost blood-red, flowers make this a stunner in the wild. The flowers are in short racemes, so it looks different from the other species which have more of a globose cluster. It has not been widely cultivated to my knowledge. My only attempt was fruitless, but I am willing to try again.

Everyone has a list or lists; I keep a list of Colorado alpine plants I have not seen or grown. Each year this list grows a bit shorter. Hopefully, in 2022, I will be able to find one or more of the following: Alicelia sedifolia, Cirsium culebraensis, Cirsium griseum var. osterhoutii, Draba grayana (confirm with a photo), Draba malpighiaceae, Luzula subcapitata, Physaria scrotiformis, and Ptilagrostis porteri.

This sizable article, for the first time, attempts to pull all the Southern Rockies endemic alpines together. This list highlights the biological importance of the Southern Rockies and the importance of the continued work towards the conservation of these special plants and areas. The West is a region whose population continues to grow at an alarming rate, gobbling up resources such as land and water. Such an increase in population has placed increasing stress on alpine areas in terms of the ever-increasing number of visitors to alpine areas and their impacts, which can trample these delicate areas. Combined with climate change this creates an uncertain future for these lovely gems.

Sources Consulted

Ackerfield, Jennifer R., et al. Thistle be a mess: Untangling the taxonomy of Cirsium (Cardueae: Compositae) in North America. Journal of Systematics and Evolution 58.6 (2020): 881-912.

Ackerfield, Jennifer. Flora of Colorado. Fort Worth: BRIT Press, 2015.

Heidel, B. 2012. Wyoming plant species of concern, April 2012. Wyoming Natural Diversity Database, Laramie, WY.

Kartesz, J.T., The Biota of North America Program (BONAP). 2015. Taxonomic Data Center. (http://www.bonap.net/tdc). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)

Kintgen, M. (2018). What Drives Species Richness in Colorado’s Alpine Tundra. Master’s Degree Thesis, Regius University, Denver, Colorado.

POWO (2022). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the internet; http://www.plantsoftheworldonline.org/ Retrieved 1-14 January 2022.

Wildflowers, Ferns, and Trees of Colorado, Arizona, New Mexico and Utah. Al Schneider Published on the internet: https://www.swcoloradowildflowers.com/index.htm/ Retrieved 21 Jan 2022.