Notes on Identifying Mentzelia species
Identification of these plants as belonging in the Mentzelia genus seems reasonably clear. But variability among plants seems to have led to a proliferation of species which differ, at most, only slightly.
Identification of Mentzelia species is shaky at best based on available references. Jepson Manual descriptions differ in confusing and inconsistent details compared with Munz and Beauchamp. Munz (A Flora of Southern California) sub-key on page 550 says "Note: the following species form a polyploid complex which can only be distinguished with difficulty; up to 5 species may grow together."). Jepson Desert Manual summary description for Mentzelia genus emphasizes that the seeds are important for identification (but of course not seen in photographs taken in the field). In two books on wildflowers in the Colorado Desert (includes Borrego area) and Mohave Desert, Jon Mark Stewart says "This group of blazing stars is one of the most variable wildflowers in the ... desert. About three or four similar species occur here and telling them apart can be quite difficult.".
Mentzelia albicaulis (or related species M.desertorum, M.dispersa,...)
I've selected M.albicaulis because the Munz description and key come closer to matching the plant shown in these photographs. The Jepson drawing of M.dispersa on page 367 looks a lot like this plant, including the acute tips on the flower petals. But the Jepson descriptions of M.albicaulis, M.desertorum, and M.dispersa lack details which might allow distinguishing these species based on the available visual information.
Mentzelia congesta (or related species M.montana, M.veatchiana,...)
This similar related plant seen at Cuyamaca Ranch differs from the above group by:
- Having the dark orange spots at bases of the petals.
- Having the flowers tightly bunched in a head at the ends of stems.
Mentzelia involucrata (or related species M.hirsutissima)
Identification here is aided by the good photo in Plate 67 of the Jepson Desert Manual.
klb