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       Lepidium montanum is highly variable and although some floras attempt to name and describe varieties, most now do not. In the words of the Flora of North America:

There is little agreement among North American authors as to the characters emphasized, the number of infraspecific taxa, their ranks, and their synonymies in treatments of Lepidium montanum.  In all, 12 varieties remain accepted in the species, and these only partially cover its overall complexity.... The characters that various authors emphasized in the delimitation of infraspecific taxa include duration, habit, plant height, indumentum density, division of basal and cauline leaves, leaf shape, and fruit size.

Indeed, the species is so highly variable in all of these aspects that the overall number of forms is mind boggling. Holmgren’s assessment that there are intermediates between the various varieties, even in areas where they do not overlap, is correct. The species is badly in need of thorough biosystematic and molecular studies to determine the number and range of infraspecific taxa, to discern the patterns of variation, and to determine how distinct the species is from the seven segregates mentioned in the previous paragraph.

A workable and satisfactory key to all of the varieties is not possible at the current stage of knowledge, and attempts to make one (e.g., Rollins, Holmgren) have been unsuccessful.

     In their third edition of Colorado Flora, Weber and Wittmann list seven varieties of L. montanum; in their fourth edition they list none and indicate, "A variable species... often divided into a number of weakly differentiated varieties". Unfortunately, neither Ackerfield's Flora of Colorado nor Allred's Flora Neomexicana III, even mention varieties or the complexity of this species. Welsh's 4th edition of A Utah Flora lists and describes eight varieties and indicates,

There is an amazing amount of variation within L. montanum.... There is justification for recognizing all of these entities at the specific level, but the convenience of having an inclusive species with several variants with overlapping morphologies seems to best represent the situation within Utah.

      Linnaeus named this genus in 1753; "lepidion" is Greek for "little scale" and refers to a scale on the seed pod. 

     Lepidium montanum, was named  by famed collector and Harvard lecturer, Thomas Nuttall, in Torrey and Gray's 1838 Flora of North America. (Click the title to read.) Nuttall was also the first to collect this plant, probably in 1834, on his trip west with the Wyeth Expedition of 1834-1837.

Lepidium montanum

Lepidium montanum

Lepidium montanum (Western Peppergrass)
Brassicaceae (Mustard Family)

Semi-desert, foothills, montane. Disturbed areas, openings. Spring, summer.
Butler Wash near the San Juan River, Utah, April 8, 2005.  Canyons of the Ancients National Monument, May 11, 2011.

Western Peppergrass is abundant in Pinyon/Juniper forests and is also common in the mountains.  One very common spring blooming variety (pictured at left and directly below) has many stems, making it almost appear to be a small shrub.  It grows two feet tall.

 
Lepidium montanum
Lepidium montanum
Lepidium montanum (Western Peppergrass)
Brassicaceae (Mustard Family)

Semi-desert, foothills, montane. Disturbed areas, openings. Spring, summer.
Butler Wash near the San Juan River, Utah, April 8, 2005.  Canyonlands National Park, Utah, April 12, 2005.
 

Lower leaves are deeply or shallowly lobed (in the top photograph at left, with few lobes, similar to a fleur-de-lis); upper leaves are usually linear.

An abundance of tiny, fragrant, white flowers is the main attraction of this very showy and common plant. 

 
Lepidium montanum
Lepidium montanum
Lepidium montanum (Western Peppergrass)
Brassicaceae (Mustard Family)

Semi-desert, foothills, montane. Disturbed areas, openings. Spring, summer.
Canyons of the Ancients National Monument, April 1, 2005.

As noted above, Lepidium montanum is a highly variable species.  The very early spring blooming variety at left looks quite different from the varieties above and below.  This variety has few stems, an open growth pattern, and grows to only a foot or so tall.  Its basal leaves have many lobes. 

Lepidium montanum

Lepidium montanum

Lepidium montanum

Lepidium montanum (Western Peppergrass)
Brassicaceae (Mustard Family)

Semi-desert, foothills, montane. Disturbed areas, openings. Spring, summer.
Near the Shiprock, New Mexico, April 5, 2016.

As noted above, Lepidium montanum is a highly variable species.  This very early spring blooming variety has many stems from the base and grows in a fairly compact, short form. Numerous plants grow in the same area, last year's flowering stems are quite evident, basal leaves wither at the time flowers appear, lower leaves (and many upper ones) are pinnate with broad, almost touching lobes, and upper leaves (see the white arrow in the third photograph) can be entire, long, and narrow. 

Lepidium montanum

Lepidium montanum

Lepidium montanum (Western Peppergrass)
Brassicaceae (Mustard Family)

Semi-desert, foothills, montane. Disturbed areas, openings. Spring, summer.
Canyons of the Ancients National Monument, August 22, 2005 and November 8, 2016.

This tall, late summer blooming variety of Lepidium montanum is very common and long-lasting in Pinyon/Juniper forest openings and along roads.  Flowers and seeds are very similar to the other L. montanums shown on this page.  Basal leaves are, however, usually withered at blooming time.  Stems may be single or multiple from the base and may branch at about a forty-five degree angle from anywhere on the stem but there are usually just a few branchings.  As a result, the plant has a very open and airy appearance and it is top-heavy with flowers and fruits that sparkle in fall sunshine.

 

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 Lepidium montanum