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Photo & ©
copyright by
Jürgen Menzel
Ariocarpus retusus forma cristata in habitat.
This plant is a rarity every cactus impassioned would like to have.
The appeal lies in the peculiarly-shaped tubercles
plus the
challenge of growing it successfully.
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Description: Ariocarpus retusus is the
largest species of the genus characterised by long tubercles slightly
projecting above ground level. The crested form is
rarer than the normal plant, and it is particularly sought after by
collectors. Also
this crest
can get quite large making a spectacular specimen.
Stem: Grey, or blue-green, flattened 10-25cm thick.
Tubercles: Leaf-like, divergent, erect,
basally compressed, usually becoming attenuate at the apices, convex or
nearly flattened
adaxially and often with shallow adaxial undulations or wrinkling,
not fissured, 1.5-4cm long, 1-3.5cm wide, nearly as wide as long;
Areoles: at the tips of the tubercles, rounded, 1-5mm in diameter.
Flowers: Diurnal 4-5cm in diameter., 2-4 2cm long; white to pink
(or magenta), occasionally with reddish midribs,
Root: Swollen and very large tap root
Flowering time: October
Fruit: white, green, or rarely pinkish, 10-25mm long, 3-10mm in
diameter.
Remarks: Ariocarpus retusus is an extremely variable species. Also crested
plants may be quite different one to each other.
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Family:
Cactaceae (Cactus
Family)
Scientific name:
Ariocarpus retusus Scheidweiler, (1838)
Pubblished in: Bull. Acad. Sci. Brux. 5: 492
forma cristata
Conservation status: Listed in
CITES Appendix I
Common Names include: Living Rock, Seven Stars
Origin: Widely distributed from north of Saltillo,
Coahuila southwards to San Luis Potosi, SLP, Also found occur in
Tamaulipas , Zacatecas and Nuevo Leon.
Habitat: High Chihuahuan desert at altitudes of between
1300 and 2000 metres, on calcareous hillsides and occasionally gypsum
plains. At lower altitudes (200 - 800m) of the Sierra Madre Oriental it
is replaced by A. retusus ssp. trigonus.
Cultivation: This species is slow growing but certainly not as slow
as some other types of cacti, it is of easy culture in a well drained,
non-organic, free-draining
soil compost, with ample water during the growing season. Use
of a weak low-nitrogen fertilizer during the
growing season can encourage growth. The main
threat to their development is root rot. Ariocarpus should be kept dry
whenever there is a threat of cold. The appearance of Ariocarpus can
benefit greatly by watering the plants from the bottom. This practice
will help to keep the “wool” on the top of the plant from becoming
matted or discoloured. Need light shade to full sun. Frost Tolerance:
Hardy to -10° C
Propagation: Cuttings, occasionally grafted.
Photo of
conspecific taxa, varieties, forms and cultivars of Ariocarpus
retusus.
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