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Pediocactus simpsonii

Pediocactus simpsonii

Pediocactus simpsonii

Pediocactus simpsonii
Pediocactus simpsonii (Simpson's Cactus, Mountain Ball Cactus)
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Summer.
Above: Sleeping Ute Mountain, May 6, 2012 and San Juan National Forest above Dolores River May 7, 2020.
Left: San Juan National Forest above Dolores River May 8, 2009.

This lovely, symmetrical ball of spines is fairly common from Sagebrush areas to the upper limits of Pinyon/Juniper forests.  Flowers are white/pink/yellow.  Spines are smooth, radial spines are white, and the central spine(s) is brown to black.  The plant shown at left is about six inches tall and seven inches wide, quite a large, but not uncommon size for Pediocactus simpsonii. When you find one Pediocactus simpsonii, look around and you will almost always find a number more. In the Four Corners region, it is also common to find several very closely packed against one another and to find the cactus growing in slab rock areas. In our area, Pediocactus simpsonii is almost always found in open areas, not obscured by other vegetation, but it is frequently overlooked because it blends into the colors and textures of its surroundings.

The Flora of North America indicates "Pediocactus simpsonii is an exceedingly variable species.... The species has the widest distribution of any Pediocactus, and is found at the highest elevation."

Pediocactus simpsonii is found in Nevada, Wyoming, and all Four Corners states, although it is rare in Arizona.  

The plant was first collected for science in Nevada by J. H. Simpson who made a number of western exploratory expeditions as a Topographical Engineer.  George Engelmann, eminent botanist and cactus expert, described and named the plant Echinocactus simpsonii in 1863.  In 1913 Nathaniel Britton and Joseph Rose created a new genus, Pediocactus, and placed this plant in it.  (More biographical information about Simpson.)

"Pedio" means "plains".

Pediocactus simpsonii

Pediocactus simpsonii

Pediocactus simpsonii

Pediocactus simpsonii (Simpson's Cactus, Mountain Ball Cactus)
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Summer.
San Juan National Forest above Dolores River, May 8, 2009 and Price's Farm, May 8, 2010.

The top two photographs at left show plants about four inches tall; the bottom plant is just an inch and a half tall.

P. simpsonii can sometimes be difficult to distinguish from Escobaria viviparaClick to read about the similarities and differences.

Pediocactus simpsonii
Pediocactus simpsonii (Simpson's Cactus, Mountain Ball Cactus)
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Summer.
San Juan National Forest above Dolores River, May 8, 2009.

Here you can see the brown central vertical spines and the mostly white radial spines.

 

Pediocactus simpsonii

                Pediocactus simpsonii

Pediocactus simpsonii

Pediocactus simpsonii (Simpson's Cactus, Mountain Ball Cactus)
Cactaceae (Cactus Family)

Semi-desert, foothills. Openings. Summer.
Northeast Arizona Navajo Reservation, June 3, 2006.

As the photographs on this page indicate, the appearance of Pediocactus simpsonii varies considerably depending on the closeness of the tubercles (the green, almost pyramid-shaped bumps) and the length of the spines. As you can see from the last two photographs at left, on young Pediocactus simpsonii, the tubercles are prominent and well-spaced from each other. Look at the other photographs on this page and you will see that as the plant matures the tubercles coalesce.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Pediocactus simpsonii