Eriogonum mortonianum

Plants shrubs, erect to spreading, not scapose, (3) 4–10 dm tall, 5–20 dm across, essentially glabrous and bright green; stems spreading, without persistent leaf bases, up to 1⁄3 height of plant, the caudex stems absent, the aerial flowering stems erect to spreading, slender, solid, not fistulose, 0.2–2 dm long, glabrous; leaves cauline on proximal 2⁄3 of stem, 1 per node, the petioles (0.2) 0.3–0.8 (1) cm long, floccose or glabrous, the blades elliptic, 1.5–4 (4.5) cm long, (0.3) 0.6–1 (1.3) cm wide, glabrous and green on both surfaces, the margins plane; inflorescences cymose, open, 15–25 cm long, 13–30 cm wide, the branches often with involucres racemosely arranged at tips of inflorescence branches, glabrous, the bracts 3, scalelike, triangular, 1–2 mm long; peduncles absent; involucres 1 per node, turbinate, 2–2.5 mm long, 1.2–1.8 (2) mm wide, glabrous, the teeth 5, erect, 0.2–0.3 mm long; flowers (2) 2.5–3 mm long, the perianth pale yellow to yellow or whitish, glabrous, the hypanthium 1⁄4 length of perianth, the tepals dimorphic, those of outer whorl obovate, 1– 1.3 mm wide, those of inner whorl oblanceolate, 0.8–1 mm wide, the stamens included to slightly exserted, 2– 2.5 mm long, the filaments pilose proximally; achenes brown, 3–3.5 mm long, glabrous. 2n = 40.

Flowering Jul-Sep. Red, gypsophilous clay flats and outcrops, mixed grassland, saltbush, and blackbrush communities; 1400–1600 m; low, gypsophilous hills west and southwest of Fredonia, Mohave Co., Arizona.

On September 5th 2014, I wrote to Jim to describe the situation west of Fredonia, (36°54’28” N / 112°35’25” W), as being not clear – at least for me. In fact, Jim went there in 1972 and 1973 and it was, respectively, beginning and mi-August. I was there 3 weeks later, in the season and, with everything blooming or starting to bloom, the botanical determination was not clear. The 3 official taxa, on the spot, are Eriogonum mortanium, Eriogonum corymbosum var. corymbosum and Eriogonum thompsoniae var. thompsoniae.

Although it is supposedly restricted to red, gypsophilous clay flats and outcrops, Walter Fertig, in June 2011, has reported the discovery of two plants of Eriogonum mortanium west of Kanab in Utah. The Kanab plants occur on rocky, reddish Moenave sandstone and clay in a Utah juniper/Two-needle pinyon community with rabbitbrush, galleta, and snakeweed.


Tepals dimorphic, those of outer whorl obovate, 1– 1.3 mm wide, those of inner whorl oblanceolate, 0.8–1 mm wide.
















On the same spot, west of Fredonia, there are two types of leaves on plants which are both Eriogonum mortanium – if we judge from the flowers which have very dimorphic tepals. Could there be hybrids between Eriogonum mortanium and/or Eriogonum corymbosum and/or Eriogonum thompsoniae?

In fact, yes, according to Reveal and Spellenberg 1976, Eriogonum mortanium readily hybridizes with Eriogonum thompsoniae var. atwoodii though these species are not closely related.







Both types side by side on September 5 th 2014 west of Fredonia (36°54’28” N / 112°35’25” W).

And there were also a few plants with white/pink perianths with the same form of leaves.




According to Reveal, Eriogonum mortonianum, is clearly related to E. smithii, however, it differs from E. smithii in that it is much larger, more highly branched inflorescence, smaller flowers and involucres, non-revolute leaves, and yellowish green stems and branches (Reveal 1974). The basic habitat of the two species is different, largely due to differences in habitat. E. mortonianum is found on reddish clay hills where the entire plant is exposed, while on the other hand, E. smithii is found in deep, moving “blow sand,” which may cover much of the plant encouraging a much more diffuse growth habit than in E. mortonianum (Reveal 1974). It is likely that past introgression with E. thompsoniae var. albiflorum has resulted in the introduction of whitish flowers in E. mortonianum and in the formation of E. thompsoniae var. atwoodii.