The Astrophytum ornatum is the largest and easiest to grow and also the fastest of the Astrophytums. Spherical when young to columnar when  mature,    some specimen develop nice twists with age.
Ribs have characteristic cross bands of wooly scales.

Family: Cactaceae (Cactus Family)

Scientific name:  Astrophytum ornatum (DC.) Weber
In: Britt & Rose, Cactaceae 3: 185. 1922

Origin: Astrophytum ornatum is the southern genus of Astrophytum. The habitats are at Hidalgo, Queretaro and Guanajuato in Mexico.

Conservation status: Listed in CITES appendix 2.

Habitat: Grows in wild canyons and limestone cliffs sometime on near vertical rockfaces .

Common English Names include: Star cactus , also known as Monk's Hood.

Synonyms:

• Echinocactus ornatus De Candolle
  In: Mém. Mus. Hist. Nat. Paris 17:114 1928
• Echinocactus mirbelii Lemaire
  In: Cact. Aliq. Nov. 22. 1838
• Echinocactus holopterus Miquel
  In: Linnaea 12:2. 1838
• Echinocactus tortus Scheidweiler
  In: Bull. Acac. Sci. Brux. 5:493. 1838
• Echinofossulocactus mirbelii Lawrence in Loudon
  In: Gard. Mag. 17:318. 1841
• Echinocctus ghiesbrechtii Salm-dick
  In: Allg. Gartenz.18:395. 1850
• Echinopsis haageana Linke
  In: Wochenschr. Gartn. Chron. 1873:983. 1873
• Echinocactus haageanus Rümpler In Förster
  In: Handb. Cact. ed. 2 469. 1885.
• Echinocactus ornatus glabrescens Shumann
  In: Gesamtb. Kakteen 324. 1898A

The Astrophytum ornatum is the largest and easiest to grow and also the fastest of the Astrophytums. Spherical when young to columnar when mature, some specimen develop nice twists with age.
Ribs have characteristic cross bands of wooly scales.

Description: A. ornatum is a shortly columnar cactus appearing star-shaped from above, with white cross bands of wooly scales. It appears to be a very variable species especially for the density and distribution of white scales. It is the largest and easiest to grow and also the fastest of the Astrophytums. It is also generally more heavily spined than other Astrophytums.
Stem: The stem is solitary, globose when young , cylindric with age, 30 to 120 cm (or more) high, 15-30 cm across, greyish-green to dark-green with more or less dense white or yellow wooly flakes in bands forming an ornate pattern.
Ribs: It has 5 to 10 (generally 8) straight or frequently spiralling, rather prominent, strongly compressed, more or less sinuate and crenate .
Areoles: 1 to 5 cm apart, at first yellowish-white felted, later grabrescent.
Radial spines: 5-11 stout, 2-4 cm long usually straight, subulated or ± laterally compressed, amber yellow, later brown and finally grey
Central spine. usually 1 rather larger.
Flowers: At apex, large, lemon-yelllow 7-12 cm broad, inner perianth segments broadly oblong, with a broad, more or less serrated apex, tube short woolly, scale on ovary, dark and very narrow.
 

The body can be dark green with very few silvery felty "scales", or can be densely covered so as to appear nearly white.

Cultivation: This cactus is pretty cold hardy and can survive to -10° C (if kept dry).  It needs to be at least 15 cm tall to bloom . This might take no less than seven years or more depending on the length of the growing period in the local climatic conditions. In the rest period no high atmospheric humidity!! Sun Exposure: Light shade to full sun.

Propagation: They can be propagated easily from seed.