A species of gypsum hills
Pediocactus sileri is an accepted species in POWO. In earlier literature it appears as Echinocactus sileri or Utahia sileri. Its sites lie along the Arizona–Utah border. The species grows on gypsiferous clay or sandy soils of the Moenkopi Formation, at 900–1600 m above sea level. [2-WWW] [Heil and Porter 2003a, POWO. Flora of North America, P. sileri]
Stem and spines near the substrate surface
The stem is solitary or sparsely branched, ranging from flattened and ovoid to elongated and cylindrical. It reaches 5–15 cm in height, exceptionally 25 cm, and 6–11.5 cm in width. There are 11–15 white radial spines, 11–21 mm long. The 3–7 central spines are 13–30 mm long, brown or black, becoming white with age. At the stem base, the spines form a dense layer in contact with the fine-grained soil. [Heil and Porter 2003a, Flora of North America, P. sileri]
Flowers, seeds and morphological distinctness
The flowers are 2–3 cm in diameter, with a yellow perianth bearing purple veins and long, fringed scales and outer tepals. The grey-black seeds reach 3.5–5 mm in length and 3–3.5 mm in width, with a tuberculate, wrinkled coat. [Heil and Porter 2003a, Flora of North America, P. sileri]
In the analysis published by Baker and Cloud-Hughes in 2022, ninety P. sileri plants from three populations served as a comparison group for 233 P. peeblesianus specimens. Seventeen stem and spine characters were measured. The sampled P. sileri remained clearly distinct in the analyses, while the former subspecies of P. peeblesianus showed broad morphological overlap. The comparison supports distinguishing the two species in this material. [Baker and Cloud-Hughes 2022, p. 303–313, tab. 4–6]
Related articles
Materials from the author's archive
The species also appears in Konrad Szychowski's private material archive. [Bydgoski Klub Miłośników Kaktusów 2002, file p. 7]
Synonyms and names in the literature
Echinocactus sileri · Utahia sileri [2-WWW]