The epidermis is smooth  and has none of the white tufted spots characteristics, giving a dark blue-green to grey-green  colour overall.
 

Description: A. myriostigma ticostatum nudum is a strikingly  pretty cultivar with only three ribs lacking or mostly lacking the white flecks that cover the epidermis of the standard myriostigma, giving it a bright green, blue-green,  gray-green or mauve-green color overall depending on clones.  
Stem: Spherical to shortly columnar with age.  The stems is smooth and can be over 50 cm tall and 5-10 cm in diameter.
Spines: None.
Ribs: 3.  This cultivar tends to be unstable, and some of the three ribbed specimens develop additional ribs as they age. Old and big plants which maintain the typical three ribbed shape are very  very prized.
Flowers: 5 cm in length, pale-yellow, silk-shining unlike the white-spotted plant, occasionally with an orange gloom.
Blooming season: Spring or early summer, They take up to 6 years to bloom.
Fruit: Dry, dehisces towards the apex forming about 5 star shaped lobes. With few seeds.
 

Only 3 fat glabrous ribs.

In full sun it has a tendency to turn into mauve hue.

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Scientific name:  Astrophytum myriostigma Lemaire
Original description: Cactacearum Genera nova Speciesque novae et omnium in Horto Monvillano cultarum: 4-6 1839

tricostatum nudum

Conservation status: Listed in CITES appendix 2.

Origin:  Japan, Garden origin (Nursery produced cultivar)

Etymology: "tricostatum"  just means it has 3 ribs. There are some other varieties of the 3 ribs, such as "nudum tricostatum", "Fukuryiu tricostatum", "Onzuka tricostatum", "Onzuka Fukuryiu tricostatum" etc.
 

Cultivation: Although regarded as a choice and difficult plant is not too difficult in a greenhouse, although grows quite slowly. It is sometime seen as a grafted plant but grows very well on its own roots too. Use mineral well permeable mineral soil with little organic matter (peat, humus). Water sparingly from March till October (weekly during summertime, if the weather is sunny enoughand) , with a little fertilizer added. keep perfectly dry in winter at temperatures from 5 to 15 degrees centigrade. (but it is relatively cold resistant and hardy to -7° (-10°)C for short periods) In the rest period no high atmospheric humidity!! They need light shade to full sun this help to keep the plants healthy, although slow growth.
 
Propagation: Almost exclusively by seed that germinate rapidly. Plants are sometimes grafted onto column-shaped cacti. Seed Collecting: Allow unblemished fruit to ripen; clean and dry seeds. Properly cleaned, seed can be successfully stored. This cultivar tends to be slower growing.
 

Photo of conspecific taxa, varieties, forms and cultivars of Astrophytum myriostigma:

• A. myriostigma
• A. myriostigma bicostatum
• A. myriostigma columnare
• A. myriostigma cv. FUKURYU (type A)
• A. myriostigma cv. FUKURYU (type B)
• A. myriostigma cv. FUKURYU (type B) nudum variegata.
• A. myriostigma cv. HAKUUN
• A. myriostigma cv. HAKUUN nudum
• A. myriostigma cv. HAKUUN nudum forma cristata
• A. myriostigma cv. HAKUUN tricostatum
• A. myriostigma cv. HUBOKI
• A. myriostigma cv. HUBUKI
• A. myriostigma cv. KIKKO
• A. myriostigma cv. KIKKO nudum
• A. myriostigma cv. LAIMAKE
• A. myriostigma cv. LOTUSLAND
• A. myriostigma maculatus forma cristata
• A. myriostigma multicostatum
• A. myriostigma nudum
• A. myriostigma nudum forma cristata
• A. myriostigma nudum forma variegata
• A. myriostigma nudum cv MAIDEN BLUSH
• A. myriostigma cv. ONZUKA
• A. myriostigma cv. ONZUKA ball type
• A. myriostigma cv. ONZUKA columnare
• A. myriostigma cv. ONZUKA cristata
• A. myriostigma cv. ONZUKA + HAKUUN
• A. myriostigma cv. ONZUKA + KIKKO
• A. myriostigma cv. ONZUKA quadricostatum
• A. myriostigma cv. ONZUKA tricostatum
• A. myriostigma cv. ONZUKA tricostatum + FUKURYU (type A)
• A. myriostigma cv. ONZUKA white form
• A. myriostigma quadricostatum
• A. myriostigma quadricostatum nudum
• A. myriostigma v. strongylogonum
• A. myriostigma v. strongylogonum cv. COSTA
• A. myriostigma tricostatum
• A. myriostigma tricostatum FUKURYU (type A)
• A. myriostigma tricostatum nudum
• A. myriostigma variegatum