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  Pediocactus simpsonii

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of Cacti and Succulents.

Pediocactus simpsonii is an extremely hardy and very variable ball cactus of mountains and prairies of north America, the spines almost completely obscure the stems.

Description: Generally singular but occasionally forming small clusters. This plant is an exceedingly variable species. a bit of variation throughout its range and some taxonomists recognize several varieties. The segregation of the many forms, varieties, and subspecies on the basis of morphology, however, is difficult to support, given the continuous range of variation in stem size and flower color over its geographic range.
Stems: Depressed-ovoid to ovoid or globular stems that are 2.5-15(-25) tall × 2.5-15 cm in diameter.
Areoles: circular to oval, villous.
Tubercles: Spirally arranged, conicalabout 5 to 15 mm long.
Spines: Located on the tips of the tubercles smooth, relatively hard, distinguishable as radial and central.
Radials: 15 to 35 widely spreading, white, slender, which are 3-13 mm long.
Centrals: 4 to 11 widely spreading about 1 to 2 cm long reddish brown (rarely black) with basal half cream or yellow, rigid, straight or slightly curved. Sometimes the spines almost obscure the surface of the plant.
Flowers: 2 to 2,5 cm, bell shaped with scales and outer tepals minutely toothed and laciniate or entire and often undulate; ranging from magenta, pink, straw-yellow, to whitish outer tepals with greenish brown midstripes. The buds and flowers originate in a small circle at the apex of the plant.
Blooming season: Open from mid April on into May. The flowers usually remain closed on cloudy days.
Fruits: Almost spherical to short cylindric 6-11 × 5-10 mm , green at first, turning tan, drying reddish brown and splitting along the side when mature.
Seeds: Gray to black, 2-3 × 1.5-2 mm, papillate but not rugose.

Photo gallery: Alphabetical listing of Cactus and Succulent pictures published in this site.

Photo gallery PEDIOCACTUS



Family: Cactaceae (Cactus Family)

Scientific name:  Pediocactus simpsonii (Engelm.) Britt. & Rose
Published in N. L. Britton and A. Brown, Ill. Fl. N. U.S. ed. 2. 2: 570. 1913 (as simpsoni).

Origin: The species has the widest distribution of any Pediocactus, and is found at the highest elevation. throughout much of the mountain in west USA (Arizona., Colorado, Idaho, Montana., Nevada, New Mexico, South Dakota., Utah, Wyoming)

Habitat: Its preferred habitat is generally higher in elevation and cooler and moister than most other cacti. This is one of the most cold-hardy species and is found as high as 1400-3500 m. These plants can be found growing in a variety of, prairie grassland, rocky steppes, sagebrush, pinyon-juniper woodland, and montane coniferous forest habitats. This cactus is frequently concealed under larger vegetation and is frequently camouflaged under plant litter and grasses. During winter dormancy it may actually shrink below the ground surface. Interestingly, the flowers are generally pink on the eastern slope and yellowish on the western slope plants.

Conservation status: Listed in CITES appendix 2.

Common Names include: Mountain ball cactus,  Simpson’s footcactus, Simpon’s hedgehog cactus

Etymology: Named in honour to the army engineer James H. Simpson who led an expedition in Colorado

Taxon synonyms

  • Echinocactus simpsonii Engelmann,
    Trans. Acad. St. Louis 2:197, 1863. (as simpsoni)
  • Mammillaria simpsonii (Engelmann) Jones,
    Zoe 3:302, 1893.
  • Mammillaria purpusii (Engelmann) Schumann,
    Monatsschr.Kakteenk. 4:165, 1894.
  • Pediocactus hermannii Marshall, Saguaroland
    Bull. 8:78, 1954.
  • Pediocactus simpsonii (Engelmann) var.caespiticus Backeberg,
    Nat .Cact. & Succt. J. (GB), 14:63, 1959. nom. nud., Cactaceae, 5:2846 f. 2672 nom. inval.1961.
  • Pediocactus simpsonii (Engelmann) var. hermannii Wiegand & Backeberg,
    Die Cactaceae 5:2846, 1961.
  • Echinocactus simpsonii var. minor Engelmann;
  • Echinocactus simpsonii var. robustior J. M. Coulter;
  • Pediocactus simpsonii subsp. bensonii (Engelmann) Hochstätter;
  • Pediocactus simpsonii subsp. idahoensis Hochstätter;
  • Pediocactus simpsonii var. indraianus Hochstätter;
  • Pediocactus simpsonii subsp. robustior (J. M. Coulter) Hochstätter;
  • Pediocactusd simpsonii var. robustior (Engelmann) L. D. Benson

Rot prone and not the easiest cactus  to grow on it's own roots in cultivation it need a well drained, porous soil is preferred. Partial shading, especially during the hottest part of the summer, is helpful. Water should be provided in late winter, early spring (the main growing season), and also in Autumn, when flower buds are produced and it starts growing again. Do not l water during the  winter seasons. Problems with this plants are most likely to result from improper watering. Too much water and the plant may rot; too little water may result in poor vigor or even death. They are good for outdoor cultivation in raised beds, rock gardens, balconies, window sills etc..

Frost Tolerance:  Winter hardy from -10° to -25° C (depending on origin)  

Propagation: Seeds: Temperature for optimum germination: night minimum approx 17 day maximum to near 40 C at any time of year with proper temperatures and daylength (ca.13-14 hours); it is possible to extend day-length with artificial lights. Anyway the seeds germinate slowly with difficulty and a low rate of success (But germiation is comparatively  easy if compared with other Pediocactus and Sclerocactus species  and often new seedling cluster spontaneously around the plant every year), scarification and stratification help, alternate freeze and thaw both wet and dry, but don’t keep wet, alternate wet and dry with changing temperature.
Germination can take several years so keep pot and try again next year. Seedlings do not do well either, and some die each year,  for this reason plants are commonly grafted on hardy stocks like Opuntia compressa in this case they are easy to grow and no special skill is required.

Photo of conspecific taxa, varieties, forms and cultivars of plants belonging to the Pediocactus simpsonii complex:

Home | E-mail | Plant files | Mail Sale Catalogue | Links | Information | Search

All the information and photos in cactus art files are now available also in the new the Enciclopedia of Cacti. We hope you find this new site informative and useful.