The Mentzelia genus is, in the words of Intermountain Flora, "a difficult group taxonomically.  [There is] a close relationship... among many of the taxa and [a] confusing array of intermediates.... The taxonomy of [most of the Mentzelias] at the level of species is beset with difficulties, and there is presently no generally accepted interpretation." 

    Stanley Welsh, author of A Utah Flora, says, "Plants in this genus are sometimes difficult to place with certainty.... The notorious variability of plant size, leaf size, shape, and lobbing, flower size, and size and shape of capsules contributes to the difficulty. Many of the features grade hopelessly into each other".

     So don't feel discouraged about not being certain of the identification of Mentzelia species. I don't. 

    The first species below, Mentzelia albicaulis, is distinct enough to feel confident about.

    Whatever the names of the plants are, they are very lovely and interesting. The flowers are bright yellow and numerous and the hairs are really special. Loasaceae leaves, buds, stems, and fruit of plants are covered with stiff, hooked hairs that cling to fingers, clothes, and fur. William Weber says: "The sandpaper surface of the leaves of Loasaceae is caused by some of the strangest plant hairs known". The hairs are longer than broad; they narrow very gradually so they look like a pagoda. Each hair is multicellular, giving the appearance of a layer cake, each layer is a translucent cell armed with a ring of two-to-six hooks. A careful look through the microscope shows that although most hooks point downward, some point straight out, some upward. All the hairs are relatively stiff. These characteristics add up to nature's Velcro.

    The Mentzelia genus was named for Christian Mentzel (1622-1701), German botanist and botanical author. (Click for more biographical information about Mentzel.)

    Click for Bob Sivinski's key to Mentzelia.

This very slender, daintier cousin of Mentzelia pterosperma (below) can be quite numerous, but because of its often minute size, it is more difficult to find. Its stem is quite light in color ("albicaulis") and its basal rosette of leaves and its flowers are small. Flowers appear at first to be pointed but after many hours they open slowly into distinctive, tubular flowers with lobed petals. Flower stems frequently nod. Plants flower from the time they are just out of the ground until they are at their maximum height of six to twelve inches tall.

"Albicaulis" is Latin for "white stemmed" and "acrolasia" is from the Greek for "summit hairs" and refers, Weber theorizes, "to hairs at petal tips".

Mentzelia albicaulis. Synonym: Acrolasia albicaulis. (Whitestem Blazingstar, Whitestem Stickleaf)
Loasaceae (Loasa Family)

Desert, semi-desert. Openings. Spring.
Lower Cross Canyon, Utah, April 11, 2017;
McElmo Canyon, Canyons of the Ancients National Monument, April 25, 2009; and
Utah near Four Corners, April 17, 2010>

Mentzelia albicaulis grows singly or in showy masses. It grows to just an inch or so high (as in the top photograph at left) or it can grow to a foot tall.

The plant has innumerable and memorable pagoda-shaped hairs that cling like Velcro. Try a leaf on your shirt.

Desert, semi-desert. Openings. Spring.
McElmo Canyon, Canyons of the Ancients National Monument, April 18, 2010.

Desert, semi-desert. Openings. Spring, summer.
Above and left: East of Aneth, Utah, May 3, 2007.

The photographs at left and above show plants at the side of a road where they receive good moisture in soils richer than those where the last two photographs below of Mentzelia multiflora were growing. The plants growing near the road are fairly consistently hardy and abundant; the plants growing on the hot slopes are much more variable in their height and abundance of flowers.

Thomas Nuttall named this species Bartonia multiflora in 1848 from collections made by William Gambel near Santa Fe along the Rio Grande (called the "Rio del Norte" by Gambel) in 1841. Asa Gray renamed the species Mentzelia multiflora in 1849.

Desert, semi-desert. Openings. Spring, summer.
East of Aneth, Utah, May 3, 2007.

Numerous seeds are in capsules 1 1/2 to 2 times longer than wide.

Desert, semi-desert. Openings. Spring, summer.
McElmo Canyon, Canyons of the Ancients National Monument, April 2, 2005.

The lobed, undulating leaves of Mentzelia multiflora are large, distinctive, and eye-catching. The stem is stout, straight, and light white/yellow. The buds are unusual in both their orange-to-green color and their open, flared tips. Plants grow to over a foot tall.

These two young hardy plants are on a hot, south facing, steep, gravelly slope that had good winter and early spring moisture.

Desert, semi-desert. Openings. Spring.
McElmo Canyon, Canyons of the Ancients National Monument, April 27, 2005.

The nearly open bud can be seen in the lower right, and a developing seed pod is just to the right of the flower. Flowers often open at night and are rarely open in sunshine.

Desert, semi-desert. Openings. Spring.
Near Sixshooter Peaks, Canyon Lands, Utah, November 15, 2021.

The lobed, undulating leaves of Mentzelia pterosperma are distinctive and eye-catching. The stem is stout, straight, and light white/yellow, as is the stem of M. multiflora shown above. Plants can grow to 1 1/2 feet. The plant shown at left was exceptionally tall at bout 15 inches.

This species was first collected for science by Alice Eastwood along Willow Creek in San Juan County, Utah, in July of 1895 and she named and described the plant in 1896.

"Pterosperma" means "winged seed", but several Mentzelia, including M. multiflora shown above, also have winged seeds.

Desert, semi-desert. Openings. Spring.
Near Sixshooter Peaks, Canyon Lands, Utah, November 15, 2021.

This was an exceptionally hardy Mentzelia pterosperma in its height, number of flowers and fruits, and late fall flowering time.

Flowers close in bright sunlight. This photograph and the one above were taken at 2:20 p.m.