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 bad about not being certain of the identification of Mentzelia species. 

    The first species below, Mentzelia albicaulis, is distinct enough to feel confident about.  The next species is probably Mentzelia pterosperma but it is possible these are Mentezlia multiflora or hybrids.

    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.  William Weber says: "The sandpaper surface of the leaves of Loasaceae is caused by some of the strangest plant hairs known".  The hairs are much longer than broad; they narrow very gradually so they look like a cell tower.  Each hair is multicellular, giving the appearance of a layer cake, each layer 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, botanical author.  (Click for more biographical information about Mentzel.)

    Click for Bob Sivinski's new key to Mentzelia.

This very slender, daintier cousin of Mentzelia pterosperma (below) is often more numerous, but because of its size, more difficult to find.  Its stem is quite light in color 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 are often only about six inches tall but do commonly grow to about a foot tall.

Click for more photographs.

    The first three photographs below show a young plant on a hot, south facing, steep, gravelly slope.  The photograph immediately above shows a plant one month later at the side of a road where it received good moisture.  I have identified both plants as Mentzellia pterosperma, but it is possible that one or more are Mentzelia multiflora.  These two species are very similar and various floral keys separate them on the basis of conflicting characteristics.  As the discussion at the top of this page indicates, this genus is in need of considerable work and precise identification of species is often difficult.