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

This is one of the rarest and highly desirable of the living rock cactus, very characteristic and unmistakable. somewhat similar to Ariocarpus, it resembles an inverted green pine cone with a woolly centre.
 

Two individuals (of the same size and age grown on 10 cm Ø Pots) showing the variable morphology of this species. The first (more typical) with broad large spaced tubercles and the second with densely packaged tubercles and numerous long yellow spines.

A young specime (5 years old)

Blooms

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( Photo and © Copyright by Marco Antonio Arroyo - Mexico )
The habitat is relatively wet, plants generally grows in limestone,  among  gravel  and   small  stone  in  the inferior part of a  dense forest on lower hill slopes in association  with  several   other  succulent  species

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Propagation: Almost exclusively by seeds. But the seedlings are tiny and very slow growing and at first  they take one or two years to reach the diameter of 3-5 mm!!!  Once they have reached 4 years old or more they are relatively easy to grow, the problem is getting them to 4 years old! Than they reach 5 cm of diameter in about 5-6 years, and require very careful watering. Plants need about 7-8   years to reach the flowering size.  
Seedlings are sometimes grafted onto column-shaped cacti to increase their growth speed.  Grafting is a much easier way of propagation than sowing.

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Scientific Name: Obregonia denegrii Frič,
In: Život v přírodě, 29(29: 14, 1925

Synonym:

• Ariocarpus denegrii (Fric) Marshall,
  In: Cact. Succ. J. Amer. 18(4):56, 1946

• Strombocactus denegrii (Fric) Rowley
  In Repert. P1. Succ. (lOS.) 23:9 (1972, publ. 1974 (without basionym date).

Vernacular name: Artichoke cactus

Conservation status: Listed in CITES appendix I

Origin: Mexico (Tamaulipas: Ciudad Victoria)

Etymology: The genus is named Obregonia to commemorate Alvaro Obregon (1880 - 1928) president of Mexico.

NOTE: This cactus is known as a "peyote" because it contained alkaloids similar to those in the well known genus Lophophora. From this reason some authors assume that the  O. denegrii  may be considered a peyote species. Extracts of this cactus have been shown to have antibiotic activity.

Habitat: Obregonia denegrii thrives both in open areas and in dense bushes in the inferior part of a dense forest on lower hill slopes where erosion is a serious problem. Sometimes plant are washed out of the ground by rain. The climate is relatively wet, plants generally grows in limestone soil, among gravel and small stone in association with several other succulent species like Agave lechuguilla, Ariocarpus trigonus, and Astrophtum myriostigma, Mammillaria baumii, Neolloydia grandiflora, Coryphantha palmeri, Echinocereus blanckii.
 

Description: Obregonia is among the most famous of all cacti for is unique artichoke-shaped stem. It is the only representative of its monospecific genus and is related to Ariocarpus. It grows almost always as a solitary plant levelled with the ground, with the sunk and woolly apex. It is considered an intermediate form between Ariocarpus and Lophophora.
Stem: Solitary, globular-squashed resembling an inverted pine cone with a woolly centre, it grows up to 15 (or more) cm in diameter and is greyish green to dark green.
Tubercles: Arising in a rosette, not imbricate, arranged in a spiral, deeply cut like an artichoke, triangular, prominent, leaf like, flat above, keeled below and with a basal ridge.
Areoles: Small at the tips of the tubercles, with wool when young.
Spines: 2 to 4 whitish to brown about 5 to 15 mm long in the young tubercles, ± soft flexible, slightly curved and often rapidly shedding.
Roots: Thick taproot.
Flower: The flowers grow between the wool of the apex, in the centre of the stem on young tubercles, they are funnel-shaped white diurnal, up to 2.5 cm in diameter, 2.5-3 cm long. External perianth segments greyish, pericarpel naked or with few scales. Filaments reddish purple or pink, anthers yellow, style white and stigma lobes white.
Blooming season: Summer.
Fruits: Hidden in the wool, pear-shaped, white naked, fleshy and edible that dry when mature. The withered flowers remaining attached.
Seeds: Large and black 1 to 1.4 mm long.
 

( Photo and © Copyright by Marco Antonio Arroyo - Mexico )
Photo in habitat
 

Old and large specimens of this species are outstandingly beautiful.

Rosette of leaf-like tubercles top this turnip-shaped cactus

Cultivation: This slow growing plant isn't always the easiest species to cultivate, but can enlarge relatively fast when well grown. It is often seen as a grafted plant but grows very well on its own roots too. Needs a very well drained mineral substratum with little organic matter (peat, humus).  Requires light sun sun to develop good compact growth and waterings should be rather infrequent, to keep the plant flat shaped and not become excessively elongated and unnatural in appearance. Use  Water sparingly from March till October and keep perfectly dry in winter, or when night temperatures remain below 10° C (but some people give this plant a light monthly watering to prevent the drying and shedding of the lower tubercles.) It is hardy to -4°C (or less)  for a short period. In the rest period no high atmospheric humidity!! Ensure  a good ventilation.

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