[Note: this page is under construction. Comments, suggestions, additions are welcome.]
14 species of Mammilaria are found in the United States, and eight are known in Arizona. We have seen only a few in our area, with one the most widespread:
"Pincushion Cactus" -- [however, note that this popular name spreads much more widely than application to this particular species alone] is found in many parts of our uplands. It is quite small -- 3 to 5 or 6 inches long, 1 1/2 to 2 inches in diameter -- but it is very drought-resistant, and presents rings of spectacular flowers that insist upon being admired by humans crossing what are often some otherwise rather barren spaces in our lands. We have some rocky hillocks that seem to be quite full of them, in fact we have named one such location "pincushion hill" to celebrate their dominance of the place -- here's one small view of it, below (thanks to Margaret McClelland):
Pincushions begin as solitary and spheroid but may branch into clusters, and they become more elongated as they grow. This type of pincushion has white radial spines long enought to overlap with those on adjacent areoles, and which almost obscure the underlying stem. The central spine (usually but not always solitary -- there may be two or three smaller ones) is dark red to nearly black, with a hooked tip.(Smaller, non-central ones are not hooked.)..
The flowers emerge on old growth, below the apex of the stem or branch, and rarely reach 2" in diameter.
Click on image below to enlarge:
Mammilaria gummifera or heyderi ("Pancake" pincushion)
This Mammilaria is much less common on our lands, is found as a solitary creature in quite scattered locations, and -- because of its very flattened aspect -- is easily missed. Typically 2" to 4" (or more) in diameter, it has a somewhat depressed apex, and its tubercles are somewhat angled or subpyramidal (see the enlarged views below). The central spine is erect (not hooked), and brown to reddish brown; the radial spines are lighter in color (some almost white), spreading out straight and from 9 to as many as 22 in number.
An indication of how inconspicuous this plant may be (when not blooming or fruiting) is provided in the image below (taken near the Jim's Willow Spring eastern fenceline on our lands in February 2004):
One can easily step on such a plant without noting its presence. A closer view resolves the plant into its interesting forms:
The depressed apex is clearly shown here at the left; note also the faint reddish tinge to some of the spines when viewed from a distance.
Click on the image at left for a close-up which shows the angularity of the tubercles. Look closely! the sub-pyramidal quality of each tubercle is not easy to make out, but is definitely there in the image.
Flowers are said to be pink, white, to cream in color, the largest petals linear-lanceolate in shape. The fruit is scarlet, fleshy, and markedly enlarged upward to as much as 11/2" long. The fruits are edible. These two images present different views of the same plant, nearly stepped on without noticing in our Northeast Corner on April 09, 2004. Click on each image to enlarge it -- you will see that both fruits and flowers appear to fit this description:
The scarcity of this plant in our area reflects the fact that we lie at the very Northwestern edge of its distribution, which runs from Cochise County Arizona to Southern New Mexico, the El Paso area of Texas and down the Rio Grande, on through an undetermined portion of Northern Mexico (says Lyman Benson, page 150). Its habitat is rocky or gravelly limestone soils at 4,000 feet or more elevation (just about what we're dealing with here on our lands).
This pair was photographed near the Cow Camp in September of 2004. These are younger plants, with brighter green and a whiter aspect to the spines, but the overall shape (including the angular tubercles) is clearly very similar to our examples above. Click on the image for a close-up view.
This Gummifera at left was photographed on the hill above the Trail Tank in May of 2004, during a very dry month. Note how the plant appears to have drawn moisture away from the surrounding soil, producing a circular cracking all around it. Click on the image to enlarge it.