The mountain ball cactus is a wide-ranging plant found throughout much of the mountain west. 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 has been found as high as 11,000 feet.

Stems: Globular stems that are generally singular but occasionally forming small clusters. Older plants can be up to 5 or 6 inches in diameter. The surface of the plant is covered with spirally arranged tubercles which are conical and about 1/4 to 1/2 inch long. P. simpsonii in sagebrush habitat at about 7,500 feet elevation in Mesa County.
Unusual crested (fasciated) form of P. simpsonii growing in pinyon-juniper habitat at about 7,500 feet elevation in Mesa County. Plant is about 13 inches across.

Spines: Areoles located on the tips of the tubercles contain 15 to 35 radial spines which are 1/4 to 1/2 inch long. Five to 11 widely spreading central spines are about 3/8 to 3/4 inches long. Sometimes the spines almost obscure the surface of the plant.

Flowers: The 3/4 to 1 inch, bell shaped flowers open from mid April on into May. The buds and flowers originate in a small circle at the apex of the plant. Flower colors range from magenta, pink, straw-yellow, to whitish. This is likely to be the earliest cactus to bloom.
	P. simpsonii in a grassland habitat at about 6,000 feet elevation in the foothills of Jefferson County. This white spined variant, known as "snowball", is about 4 inches in diameter.
P. simpsonii in pinyon-juniper habitat at about 6,500 feet elevation in Mesa County. Plant about 5 inches in diameter.	P. simpsonii in cultivation in Mesa County. Plant about 3 inches in diameter.

Fruits: The 1 1/2 inch long fruits are almost spherical. They are green at first, turning tan and splitting along the side when dry and mature.

Habitat: These plants can be found growing in a variety of, grassland, sagebrush, pinyon-juniper woodland, and montane forest habitats.

Comments: 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. This plant shows quite a bit of variation throughout its range and some taxonomists recognize several varieties.

Culture: A well drained, porous soil is preferred. A desert rock garden with lots of additional coarse sand and gravel is ideal. Partial shading, especially during the hottest part of the summer, is helpful. Supplemental water should be provided during the growing season when the plants are getting established and during extended hot dry periods. Do not add any supplemental water during the fall and winter seasons. Light annual applications of a well balanced fertilizer may improve plant vigor and flowering.

Propagation: Growing from seeds is the most effective way of propagating the mountain ball cactus. Seedlings should be pot grown until they are at least 3/4 inch diameter. Moderate shading should be provided for the seedlings.

Problems: There are few insect or disease pests associated with most hardy cacti. Problems 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.

References Used

The Chinle Cactus and Succulent Club