Click to read about the Erigeron genus.

    The two Erigerons shown on this page are very similar and appear next to each other in botanical keys.  Although the seeds provide a good method for distinguishing between the two (the seeds of E. argentatus have 6-8 veins; those of E. utahensis have 4 veins [rarely 6]), this is not a very noticeable or easily observable feature.  Look first for the basal leaves.  As shown in the photographs below, the basal leaves of E. argentatus form a tidy, dense, and often small mound (3-6 inches in diameter).  The basal leaves of E. utahensis are often withered at flowering time ("anthesis"), the lower area of the plant looks raggedy, and the basal area is often 3-12 inches in diameter. 

     When you look at the basal leaves also look for dried stems from last year.  E. argentatus has no stems from last year; E. utahensis commonly has dried stems from last year.

     Several other less clear-cut characteristics can sometimes assist in separating the two species:

1) E. argentatus grows at 4,000-7,500 feet in elevation; E. utahensis grows at 3,000-6,000.

2) E. argentatus typically has solitary heads; E. utahensis often has solitary heads but can have few or many.

3) E. argentatus typically grows from 4-12 inches tall; E. utahensis grows from 4-20 inches tall.

     It is often thought that one key characteristic that separates Erigerons from other genera of Asteraceae is that Erigerons have phyllaries (the bracts that surround the base of the flower head) all in one row.  It is worth noting that both species on this page have phyllaries in several rows.

Semi-desert.  Shrublands.  Spring.
Above: Canyons of the Ancients National Monument, May 21, 2013.
Left: Blackrock Canyon, Navajo Reservation, Arizona, May 12, 2007.

This silvery ("argentatus") gray-green Erigeron inhabits dry, open lands.  It is found in Colorado, New Mexico, and Arizona in just the counties bordering the Four Corners, but it is found in most counties of Utah.  Erigeron argentatus was found in Colorado only in the early 21st century, first on the Ute Mountain Ute Reservation by Leslie Stewart and later I found it just north of the Ute lands in Canyons of the Ancients National Monument.

Ray flower color ranges from infrequent whites and pinks to pale blues and lavenders.  Basal leaves are tightly clustered and several inches long.  Stem leaves are fewer and shorter. Notice that dead basal leaves persist beneath the new growth.

The plant was named and described in 1873 by Asa Gray from a specimen that his student, botanical associate, and successor, Sereno Watson, found in Nevada.

Semi-desert.  Shrublands.  Spring.
Blackrock Canyon, Navajo Reservation, Arizona, May 12, 2007.

The phyllaries are sharply pointed, in 3-4 rows (although some specimens found in Canyons of the Ancients have phyllaries nearly equal in length), and they (and the leaves) have silvery-strigose hairs, i.e., the hairs are sharp-pointed, straight, and appressed.  Some of the hairs are unusual in that they are bent backward near their tips, i.e., they are "antrorse".  You can see this feature in the involucre close-up photograph along the very left edge.

Semi-desert.  Shrublands.  Spring.
Blackrock Canyon, Navajo Reservation, Arizona, May 12, 2007.

Semi-desert.  Shrublands.  Spring.
Canyons of the Ancients National Monument, May 21, 2013.

Leaves are densely strigose giving the appearance of a sage-green color.

Semi-desert. Canyons, shrublands, woodlands, rocks.  Spring, summer.
Corona/Bow Tie Arches Trail, Utah, May 27, 2016.

Semi-desert. Canyons, shrublands, woodlands, rocks.  Spring, summer.
Near Colorado River by Moab, May 5, 2005.

Numerous stems typically form clusters of Erigeron utahensis about eight inches in diameter at their base and a foot tall but the plant may be as much as three feet across and two feet tall or as little as several inches in diameter and only eight inches tall.  Last year's dried stems are usually present.  The plant is strikingly apparent on bare rock where it often grows in small, sandy crevices. 

Asa Gray named this species Erigeron stenophyllum in 1873 from a specimen collected by Mrs. A. P. Thompson near Kanab, Utah.  Arthur Cronquist, lead author of the Intermountain Flora, renamed it Erigeron utahensis in 1947. Cronquist indicated that there are two varieties of E. utahensis: variety utahensis and variety sparsifolius. These taxa are very similar, differing primarily in the degree of pubescence of the stems, the length of the stem leaves, the size of the flower head, and the date of flowering. Welsh's A Utah Flora agrees with these distinctions, as does John Kartesz, the ultimate authority for all plant names on this website. However, the prestigious Flora of North America gives these two taxa species status: E. utahensis and E. sparsifolius.

Semi-desert. Canyons, shrublands, woodlands, rocks.  Spring, summer.
Near Colorado River by Moab, Utah, May 5, 2005 and Hidden Valley Trail, Moab, October 21, 2013.

Flower color is sometimes intense in the bud stage, becoming much more subdued as the flower fully opens. This change in color is fairly common in a number of Erigerons.

The second and third photographs at left show a fairly common occurrence: spring blooming plants re-blooming in the fall when conditions are favorable. However, as is also common, the fall flowers are considerably smaller and fewer in number than the spring flowers.

The second photograph also shows the numerous green stems from 2013 growth and the even more numerous buff stems from 2012. The smaller flowers and fewer stems are due to the spring and summer drought of 2013.

Semi-desert. Canyons, shrublands, woodlands, rocks.  Spring, summer.
Near Colorado River by Moab, May 5, 2005.

The 10-40 ray flowers can vary from one to nearly three millimeters wide and four to eighteen millimeters long, quite a variation. 

Color also can vary widely from blue to pink to white.  This color variation and change in color from buds to fully developed flower is typical of the ray flowers of many Erigerons.  

Semi-desert. Canyons, shrublands, woodlands, rocks.  Spring, summer.
Canyons of the Ancients National Monument, May 26, 2011.

A number of keys indicate that the stems are "grayish or silvery" or "gray-green to whitish" but the plants I find in the Four Corners area and many shown on-line from herbaria, are distinctly green with easily observed strigose hairs which do sometimes grow so thickly that the stem appears dotted or pitted  --  until you look at the stem with your magnifying glass and then you see the silvery hairs.

Phyllaries, too, are hairy and they are commonly red tipped.

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 Erigeron argentatus

Range map for Erigeron utahensis