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Ariocarpus kotschuobeyanus ssp. mcdowellii (SB283 Dr Arroyo, Nuevo Leon, Mexico )
These are the northern populations  of the species; they are smaller than the type, with small beak-like tubercles and pale mauve flowers, often with a high white content in the outer petals.
 

Description: A. kotschoubeyanus are very flat geophyte cactus that produce small star-shaped rosettes. They in most cases don't reach more than only a few centimetres above the ground. Although they can form clumps, often only a small disc of tubercles can be seen flat at the soil surface, however these plants grow a large tap root below the surface of the compost.
Stem: Usually solitary, rarely giving rise to side shoots from old areoles, flattened on top, depressed centrally.
Tubercles: The tubercles are deltoid dark olive green  with no spines and lie flat on the soil surface. They are more long than wide, closely packed and divergent, sharply angled apically.
Areoles: The tubecles forms a central longitudinal areolar groove extending to the tips on the adaxial surfaces of the tubercles, woolly, 1-3 mm wide, 5-10 mm long. 
Root:  Each plant has a large turnip-like taproot, which lies below the soil surface and serves for water storage.
Flowers: These plants have a  woolly  crown, from which emerge bright pink-violet flowers up to 2.5-5 cm, 2 times wider than long when fully expanded. Flowers are diurnal and last for 3 to 4 days. The white-flowered variety was described as var. albiflorus.
Blooming time: Mid-September onwards.
Fruits:  White or green with lots of seed.

A. kotschoubeyanus is a variable species:
As with most other widely distributed species of this genus there appears to be geographical clines, in this case a north - south cline and a west - east cline.
The plants in northern populations (known as A. kotschoubeyanus. var. macdowellii) are smaller than the type, with small beak-like tubercles and pale mauve flowers, often with a high white content in the outer petals.
In contrast the southerly form ( known as A. kotschoubeyanus var. elephantendens) are much larger with larger, highly textured, triangulate tubercles, and a deep purple flower with little or no white content.
A. kotschoubeyanus ssp. sladkovskyi differs from the other red flowering A. kotschoubeyanus (that have a dull and rough epidermis) for having a smoother and shiny epidermis.
A small growing form with white flowers (known as A. kotschoubeyanus var. albiflorus) has been described in Tamaulipas.
The type species is intermediate between all the above forms and is to be found off highway 80, between El Huisache Junction and Santo Domingo.
 

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Conservation status: Listed in CITES appendix I

Synonyms:

• Ariocarpus macdowellii Marshall In Marshall and Bock,
  Cactaceae 135 (1941), nom. nud

• Roseocactus kotschoubeyanus (Lem.) Berg. var. macdowellii (Marsh.) Backbg.,
  Cactaceae 5:3075 (1961)

Origin: Mexico, A. scapharostrus  is widely distributed as a large number of small, isolated populations in a big area extending over 600 km, from central Coahuila in the north to Queretaro in the south, and the species is also found in the states of Zacatecas, San Luis Potosi, Nuevo Leon and Tamaulipas.

 A. kotschoubeyanus. var. macdowellii is the northern population of the species
 

It is very flat and does in most cases not reach more then only one cm above the ground  and only a small disc of tubercles can be seen flat at the soil surface, however these plants grow a large tap root below the surface of the compost.

Cultivation:  The plants need deep pots to accommodate the napiform unit formed by the stem base and the rootstock , and a loose mineral soil with a well-drained substrate. They need a good amount of light.   A place near the roof of the greenhouse helps, drying the pot after watering.  This can be done weekly during the summertime, if the weather is sunny enough, with a little fertilizer added.  Kept this way, plants will show a healthy, although slow growth. They are frost hardy to -10°C.
Propagation: By seeds, remembering that  seedlings dislike strong light and dry conditions  and need to be repotted frequently. Eventually, as they become mature, they attain a maximum size of 5 to 9 cm. But plants are often grafted to accelerate growth as they would generally take at least a decade to reach maturity on their own, but the grafted plants are typical rather tall growing, compared with plants on their own roots, that are usually very flat to the ground.

Photo of conspecific taxa, varieties, forms and cultivars of Ariocarpus kotschoubeyanus:

• Ariocarpus kotschoubeyanus
• Ariocarpus kotschoubeyanus forma mostruosa
• Ariocarpus kotschoubeyanus forma prolifera
• Ariocarpus kotschoubeyanus var. albiflorus
• Ariocarpus kotschoubeyanus var. elephantidens
• Ariocarpus kotschoubeyanus var. macdowellii
• Ariocarpus kotschoubeyanus var. sladovski

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