Pediocactus simpsonii looks like a Mammillaria species but its flower blooms near the apex. That is a impression of P.simpsonii for many cactus lover. However, particular feature of this species is that they are adapted to the cold environment of high altitude. P.simsonii is distributed almost all over states of western US, from high mountain of New Mexico and Arizona in southern part, near Canadian border of Washington and Montana in northern part. The area is really vast. And also they extend their habitat from Sagebrush Desert into high mountain forest of Rocky over 3000m. They endure -10 to -25c or lower in winter sometimes covered with snow. The place they live is not always 'desert' we think cactus country should be. We can find them in deep forest, high trees of oak or pine where we can not walk around without compass! Therefore the environmental factors of such a kind of habitat are the points to be specially considered in cultivation. They have a feature of 'alpine plant' in one aspect.
Because they live in various environments on vast area, the range of variation is also very large. Plant body, size, spination, flower color are variable. In some locality plants grow thick and large like 'spiny bascket ball'. On the other hand small 'mimicry type' plant is almost buried in the ground.
About this species, there are some different views of classfication still now among researchers. The general opinion is that the basic species includes some subspecies. Or some ssp is regarded as independent species by some expert. In horticulture, what is necessary may be just to enjoy various 'faces' from many localities, and collecting the plants with 'field number'. An example of a classification is below;
　　
　　
Pediocactus simpsonii ssp. simpsonii 　　　
Basic species. growing to 15cm at the maximum, but in some locality only several centimeters.
Plants are distributed from Montana, Idaho, Wyoming, Colorado, Utah, Nevada, New Mexico, Arizona. They are adapted not only forest-environmen but also Prairie-environment.
A certain type from Idaho is called ssp.indraianus.

Pediocactus simpsonii ssp. minor.　　　　　
The difference from basic species is not clear. Plants have more small body and delicate spine.. Distribution area is higher altitude than basic species, in Wyoming, Colorado, New Mexico.

Pediocactus simpsonii ssp. nigrispinus　　　
Plants with larger-sized body than basic species, often make a large clump. They are armed with the strong and darker colored spines look like Ped.sileri. They live mostly in volcanic soil of western states, Washington and Oregon. They have tap roots for adaptation to such a kind of soil.
ssp.puebloensis is from 'alpine tundra' near the altitude 2000m of Oregon

Pediocactus simpsonii ssp. robstior　　　　
Plants are similar to ssp.nigrispinus but they are distributed only in Nevada, 2000m or more in altitude.They don't have tap roots.


I have visited only a few locality still now and this page is also incomplete. I would like to introduce more pictures from various habitats in near future.

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