The several taller Mertensias of the Four Corners area are clearly differentiated from each other and are fairly easy to identify. Click to see M. franciscana and M. ciliata.

      The shorter Mertensias are not clearly differentiated from each other and they are quite difficult, perhaps impossible to identify using most keys, but in 2014 the Mertensia genetic work of Nazaire and Hufford led to a better understanding of this difficult genus. Nazaire and Hufford's work was followed by new keys such as the one in 2020 by Jennifer Ackerfield.

In the following paragraphs I outline the confusion that has existed for well over a century:

      Below you will find the Mertensia key developed by Louis Otho Williams for his PhD in 1935. That key forms the base for almost all succeeding keys.

     Botanical treatments of Mertensia agree in their initial separation of the genus:

1) Plants over 4 dm (16")
evident lateral leaf veins
flowering in late spring and summer
typically in moist sites
M. arizonica, M. ciliata, and M. franciscana

In the Four Corners area Mertensia arizonica is recorded only from San Juan County, Utah, and I have not seen this plant. Click to see M. franciscana and M. ciliata which occur commonly in our area.

2) Plants less than 4 dm (16")
usually without evident lateral leaf veins
flowering as soon as snow melts and temperatures permit
typically in open fairly dry sites
Mertensias: M. bakeri, M. brevistyla, M. fusiformis, M. lanceolata, M. oblongifolia, and M. viridis. 

     Unfortunately there is considerable disagreement about the characteristics of these shorter Mertensia and whether all are distinct species. 

     Weber lists M. brevistyla (giving the synonym M. fusiformis), M. lanceolata (giving synonyms M. bakeri and M. viridis), and M. oblongifolia. 

     Intermountain Flora lists M. brevistyla, M. oblongifolia, M. fusiformis (stating that M. fusiformis is "hard to separate from Colorado's M. lanceolata"), M. viridis (with synonyms M. bakeri and M. lanceolata var. viridis).

     Welsh describes M. brevistyla, M. fusiformis, M. lanceolata, M. oblongifolia for Utah and makes no comment about the difficulty of separating them from one another or about M. bakeri and M. viridis.

     Flora of the Four Corners Region describes only M. fusiformis and M. lanceolata (indicating that M. lanceolata var. nivalis is the same as M. viridis) but makes no mention of M. brevistyla, M. oblongifolia, or M. bakeri.

    Allred's Flora Neomexicana III includes only M. brevistyla (giving a synonym of M. fusiformis) and M. lanceolata (giving a synonym of M. viridis). Allred does not mention M. bakeri or M. oblongifolia.

     Kartesz lists M. brevistyla, M. lanceolata, M. oblongifolia (synonym M. fusiformis), and M. viridis (synonym M. bakeri ).

    Harrington's Manual of the Plants of Colorado lists all six species discussed above and indicates, "The writer is following Williams... as the latest broad treatment with the realization that the result is often unsatisfactory in Colorado".

    Summary: Of the above seven authors, only Harrington accepts M. bakeri as a species; M. viridis gets just three votes; M. fusiformis and M. oblongifolia each get four votes and M. brevistyla and M. lanceolata each get six votes.

     Given the significant lack of agreement outlined above, what are professional and amateur botanists to do with the small Mertensias?

     Louis Otho Williams worked on this problem in the early 1930s and published his 1935 Washington University PhD dissertation in the Annals of the Missouri Botanical Garden in 1937. Click to read.

     Williams accepts all 6 of the smaller Mertensias discussed above. His phrasing and parts of his key are used by all the above authors but none accepts all six of his species.

     Following is Williams' key to the 6 species we have been discussing. Other species included in Williams' key are omitted.

     Williams starts by separating the shorter Mertensia from the taller and describes the shorter as follows:

Plants usually without lateral veins in the cauline leaves...; stems usually less that 4 dm tall; normally flowering in early spring, later when growing in the mountains, but commonly as soon as the snow and temperature permit; mostly occurring in fairly dry open habitats or if in the mountains often in moist or wet situations.

A. Filaments attached in the corolla-tube, the anthers not projecting beyond the throat, i.e., contained within the tube.
          Leaves pubescent on the upper surface, glabrous below. Backs of the calyx-lobes and the stems pubescent; plants not alpine or subalpine .....M. brevistyla

AA. Filaments attached near the throat of the corolla-tube, anthers projecting beyond the throat, i.e., not contained in the tube.
     C. Limb of the corolla longer than or subequal to the tube.
        D. Leaves strigose only above or glabrous on both surfaces.
            E. Filaments shorter than the anthers; calyx divided quite to the base; style usually not reaching the anthers; anthers straight; leaves strigose above; plants usually alpine or subalpine, sometimes of lower elevations and then more densely strigose .....M. viridis

            EE. Filaments longer than the anthers; calyx not divided quite to the base; style usually reaching or surpassing the anthers; anthers usually curved; leaves strigose above or glabrous; plants usually not alpine or subalpine.
                     H. Roots fusiform; calyx pubescent on the back; leaves usually densely strigose above, the hairs directed toward the nearest margin of the leaf .....M. fusiformis                     
                     HH. Roots not fusiform; calyx glabrous on the back; leaves glabrous to rather densely strigose on the upper surface, the hairs usually directed toward the apex of the leaf .....M. lanceolata

        DD. Leaves pubescent on both surfaces.... Leads to M. lanceolata if calyx is divided 1/2 way to base and to M. lanceolata if divided 2/3 the way and has linear to lanceolate leaves and is a plant of the plains or to M. viridis if it has narrowly ovate leaves and is a plant of the high mountains.

   CC. Limb of the corolla shorter than the tube.
                M. Tube of the mature corolla only slightly longer than the limb. Leaves pubescent on both surfaces. Leaves not unilateral [not all on one side], usually larger than those of M. viridis. Calyx usually densely pubescent on the back and margins; pubescence of the upper surface of the leaves appressed .....M. bakeri
                MM. Tube of mature corolla usually much longer than the limb; plants on plains or low hills. Leaves usually acute and more than three times longer than broad. Leaves pubescent above, glabrous below .....M. oblongifolia

      In 2014 Nazaire and Hufford made another attempt at understanding the Mertensia genus in their "Phylogenetic Systematics of the Genus Mertensia (Boraginaceae)". As the second paragraph below indicates, their research provides a new understanding of species relationships within Mertensia. Although Nazaire and Hufford provided no dichotomous key, other botanists immediately began working on such keys. Using Nazaire and Hufford's research, Jennifer Ackerfield, author of the Flora of Colorado, in 2020 constructed a revised key to the Mertensia of Colorado.

Nazaire and Hufford indicate, 

No comprehensive molecular phylogeny has been conducted for [Mertensia]. We present a study of the evolutionary relationships within Mertensia using molecular phylogenetics that offers extensive sampling of exemplars of previously proposed names and populations across their geographic distributions based on the taxonomic treatments by Macbride (1916), Williams (1937), and Popov (1953a, 1953b). Specifically our four main objectives are to (1) infer evolutionary lineages and identify major clades within Mertensia; 2) test whether previously hypothesized subgeneric groups and relationships among species are monophyletic; (3) use our molecular phylogenetic hypothesis to address problematic taxonomic circumscriptions; and (4) discuss the variation of morphological characters in light of the phylogeny of Mertensia.

Our results contrast with those hypothesized prior phylogenetic studies, pointing toward a new understanding of species diversity in Mertensia and insights into its long-standing taxonomic controversies.

Foothills, montane.  Woodlands, meadows, openings.  Spring, summer.
Cross Mountain Trail, June 12, 2006.
Mesa Verde National Park, May 9, 2007.

As indicated above, expert botanists do not agree on the identification of the various short Mertensias. I have been calling the plant shown in these photographs Mertensia brevistyla, but using Williams' key (see above) and Ackerfield's key, the plants key to M. fusiformis: the filaments are longer than the anthers, the filaments are attached at the junction of the tube and limb, the style comes just to the limb, the tube and limb are about the same length. And the root is fusiform (spindle shaped, i.e., tapering at both ends and wide in the middle). Most, but not all these characteristics fit M. fusiformis, but they fit that species better than they fit M. brevistyla.

I should also note that the superb Intermountain Flora gives morphological characteristics and drawings of M. fusiformis that fit the photographs shown here.

Foothills, montane.  Woodlands, meadows, openings.  Spring, summer.
Cross Mountain Trail, June 12, 2006.

M. lanceolata, shown below does not occur in Utah or Arizona.  M. fusiformis does not occur in Arizona and is found in just a few north-western counties of New Mexico.  Both plants occur primarily in the mountains of Colorado but M. lanceolata is also found northward in Wyoming, Montana, and the Dakotas.

Mertensia fusiformis was named by Edward Greene in 1899 from a specimen collected by Baker, Earle, and Tracy in the West La Plata Mountains of Colorado.

Foothills, montane.  Woodlands, meadows, openings.  Spring, summer.
Cross Mountain Trail, June 12, 2006.

Numerous, short, flattened hairs pointing away from the prominent mid-vein of the leaf are key identifying characteristics for M. brevistyla -- according to Weber. But according to Williams these hairs are a key characteristic of M. fusiformis. Ackerfield agrees with Williams.

Foothills to alpine.  Woodlands, meadows, openings.  Spring, summer.
Above: Kennebec Pass area, August 14. 2019 and Cross Mountain Trail, August 5, 2019.
Left: Cinnamon Pass, July 26, 2007; Cross Mountain Trail, June 30, 2010; Sharkstooth Trail, June 24, 2014.

Mertensia lanceolata is, in William Weber's words, "a quite variable and complex species separable into alpine and lowland, pubescent and glabrous, broad- and narrow-leaved races, all evidently merging and recombining in puzzling ways."  The photograph at top left shows some of the "puzzling ways" with quite broad leaves topped by quite narrow leaves. Other photographs at left, above, and below show the variations in leaf hairiness, from glabrous (smooth, not hairy) to densely strigose (short, appressed, pointed hairs).

Mertensia lanceolata is typically 8-14 inches tall, and it grows singly or in clusters, generally in greater numbers than Mertensia fusiformis. Although it can spread into colonies to about two feet in diameter, it does not grow in the massive numbers that characterizes M. ciliata.

Although Weber indicates that Mertensia lanceolata grows at low elevations, in the Four Corners area it is usually found at high sub-alpine and alpine elevations. 

Bradbury discovered this plant for science in the early 1800s and Frederic Pursh named the plant Pulmonaria lanceolata in 1814. Augustin de Candolle renamed it Mertensia lanceolata in 1846. "Lanceolata" refers to the leaf shape. 

Foothills to alpine.  Woodlands, meadows, openings.  Spring, summer.
Eureka Gulch, July 18, 2009.

Foothills to alpine.  Woodlands, meadows, openings.  Spring, summer.
Cinnamon Pass, July 26, 2007.

Mertensia  lanceolata alpine flowers often have varying iridescent blue hues. It is common to find small clumps of plants, rather than individual plants.

Foothills to alpine.  Woodlands, meadows, openings.  Spring, summer.
Colorado Trail near Hillside Road, August 4, 2014.

Mertensia  lanceolata leaf surfaces vary from glabrous to such hairiness as shown at left. When hairs are present they are strigose. Those on the upper surface of leaves often all point toward the tip or may be as shown at left: pointing in various directions with most pointing toward the tip. Hairs on the under side usually uniformly point toward the tip.

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

Range map for Mertensia fusiformis

Range map for Mertensia lanceolata