La forma "dadakii"  è globosa con l'apice depresso, ha circa 12 costolature e ramifica alla base e formando piccoli cespi con molte teste. Le spine sono 8 tutte radiali, piegate verso il corpo e contorte, brune che diventano bianche invecchiando.

Family: Cactaceae (Cactus Family)

Frailea pygmaea var. dadakii (Frič) Backeberg
In: Die Cactaceae, 3: 1659, 1959

Accepted Scientific Name: Frailea pygmaea
An. Mus. Nac. Buenos Aires III.4:497, 1905

Echinocactus dadakii Frič
In: Praktický rádce pro zahradnictví a chov drobného zvířectva, 17: 65, 1922
Frailea dadakii (Frič) Berger
In: Kakteen, p. 218, 1929

Distribution: Widespread over a wide area in Brazil, Uruguay and Argentina.

Habitat & ecology: Grows often in mountainous region in scattered but numerous populations, and it is often quite common. Usually it is found in the crevices of rocky outcrops, between the pebbles near these outcrops or in grassy, gravelly areas where the thin soil depth minimizes any competition from other plants. It is often found growing together with F. gracillima and F. castanea. The rain fall are quite frequent and often abundant.

Conservation status: Listed in CITES Appendix II

Etymology: The genus name "Frailea" remembers the Spanish "Manuel Fraile", born in 1850 who was responsible for the cactus collection of the Department of Agriculture of the United States at the end of the XIX century.
The species name name "pygmaea" derives from the Latin name “pygmaeus” which means “dwarf” and refers to the very deminute dimension of this plant. ( The specific name implies: "very dwarf").

Frailea pygmaea v. dadakii 

Description: Frailea pygmaea as the name implies ("pygmaeus" meaning dwarf), is a very small cactus that lives half buried in the ground. Most of the plants in habitat are single headed unless they are damaged.
Root: Long tuberose, inversely conical 2-3 cm wide.
Stem: Typical F. pygmaea has a flattened, light green to dull green body, depressed at the crown, , with a turbinate base, 1 to 3 cm in diameter. Some forms have distinctive dark crescent-shaped marks below the areoles.
Ribs: 13-21 ribs, quite flat divided by transverse depression into tiny tubercles (more noticeable when the body is dehydrated).
Areoles: At first with witish or slight yellow wool.
Spines: 6 -10 quite fine, short, bristly, setaceous, glassy, white radial spines, 1- 4 mm long, adpressed and rarely also one or two small central spines. They are straight or slightly curved. Some forms have longer white spines that are basally orange yellow in colour while other have yellow spines and wool.
Flowers: Arising from the crown from a very woolly bud, often cleistogamous, 2 to 2.5 cm, up to 3 cm diameter, pale yellow, with dense, whitish to rose-colored pubescence outside. Inner perianth-segments lanceolate, acute, yellow; filaments and style white; stigma-lobes yellowish. But don't be disappointed when the easily produced buds fail to open. Fraileas are cleistogamous meaning that their flowers produce seed without even opening. Without the need for pollination, hence the buds rarely reach full bloom and remain closed. They will open only in great heat in the hottest, brightest, afternoon sun, if at all.
Blooming season: Hottest part of summer.
Fruit: Dry  indehiscent that detach easily, pear-shaped, 1,5 cm tall, 1 cm in diameter, with short matted hairs and with a pointed head of bristles. The fruit wall is thick, membranous, fragile and it opens by a basal pore to release the seeds that are promptly harvested by ants.
Seeds: Elm shaped, 2 mm. long, shining, black with large oblong hilum nearly as long as the body.

The "dadakii" form  is globular, depressed on top, with about 12 ribs. It branches profusely from the base forming soon dense clumps. The spines are all radial, usually 8, brownish passing to white, curved backwards and twisted.

Cultivation:  Grow them in rich, porous soil and let them dry out between waterings.  These plants need a minimum temperature of 5-10° C (but occasionally temperatures of a few degrees below 0° are not dangerous)
Sun Exposure: They enjoy full sun but in a shaded position the plants grow faster, but are not  flat shaped.
Characteristically, during the dry season plants retract completely under the ground both in the wild and in cultivation too.
Notes: This plant is short living (It does not live long - about 10-15 years).

Propagation:  With fresh harvested  seeds.

NOTE: F. pygmaea has a wide distribution and is very variable with some forms having heads no wider than one or two centimetres. In accordance with the variability of the species, many names have been created for different forms, some of them correctly published but the majority invalidly and nowadays considered  as synonyms:

• Frailea pygmaea ssp. albicolumnaris (F. Ritter) A. Hofacker,
  Cactaceae Consensus Initiatives 6: 11, 1998
  This is the most distinctive variation, and the only one accepted at infraspecific rank that grows in Rio Grande do Sul, it is  a stouter form up to 4 cm in diameter and 8 cm in height, distinguished by the glaucous greyish-green epidermis and the tendency to become columnar, also it has many straight and vertical ribs not broken into tubercles.
• Frailea pygmaea ssp. altigibbera (F. Ritter) P.J. Braun & E. Esteves Pereira
  Succulenta (Netherlands) 74 (3): 131, 1995
• Frailea pygmaea ssp. asperispina (F. Ritter) P.J. Braun & E. Esteves Pereira
  Succulenta (Netherlands) 74 (3): 131, 1995
• Frailea pygmaea ssp. aureinitens (A.F.H. Buining & A.J. Brederoo) P.J. Braun & E. Esteves Pereira
  Succulenta (Netherlands) 74 (3): 131, 1995
• Frailea pygmaea ssp. aureispina (F. Ritter) P.J. Braun & E. Esteves Pereira
  Succulenta (Netherlands) 74 (3): 131, 1995
• Frailea pygmaea ssp. fulviseta (A.F.H. Buining & A.J. Brederoo) P.J. Braun & E. Esteves Pereira
  Succulenta (Netherlands) 74 (3): 131, 1995
• Frailea pygmaea ssp. hyssooniana K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 83, without latin descr. or type, 1997
• Frailea pygmaea ssp. lilalunula (F. Ritter) P.J. Braun & E. Esteves Pereira
  Succulenta, 74 (3): 131: 1995
• Frailea pygmaea ssp. pygmaea
• Frailea pygmaea ssp. tuyensis Metzing
  Cact. Syst. Init. No 21: 16
• Frailea pygmaea var. aceguaensis K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 103, without latin descr. or type, 1997
• Frailea pygmaea var. albispina
• Frailea pygmaea var. altigibbera Ritter
  Kakteen in Südamerika, Vol.1, 203, Spangenberg 1979
• Frailea pygmaea var. applanata K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 81, without latin descr. or type, 1997
• Frailea pygmaea var. argenta K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 87, without latin descr. or type, 1997
• Frailea pygmaea var. atrofusca Backeberg
  Kaktus-ABC 250. 1935 Without Latin diagnosis; Cactac. 3:, 1935
• Frailea pygmaea var. aurea (Backeberg) Backeberg
  Cactaceae (Backeberg) 3:, 1959
• Frailea pygmaea var. auricantha K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 81, without latin descr. or type, 1997
• Frailea pygmaea var. bagensis K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 102, without latin descr. or type, 1997
• Frailea pygmaea var. brunneo mollispina
  (Zaadlijst 2006 CaVe)
• Frailea pygmaea var. carpinteria K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 78, without latin descr. or type, 1997
• Frailea pygmaea var. castaneoidea K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 79, without latin descr. or type., 1997
• Frailea pygmaea var. catiensis
• Frailea pygmeae var. corallima
  (Zaadlijst 2006 CaVe)
• Frailea pygmaea var. corallina K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 82, without latin descr. or type, 1997
• Frailea pygmaea var. curvispina F. Ritter
  Kakteen in Südamerika, 1: 204, 1979
• Frailea pygmaea var. dadakii (Fric ex Berger) Backeberg
  Cactaceae (Backeberg) 3:, 1959
• Frailea pygmaea var. elegantissima
• Frailea pygmaea var. gemmrichii K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 98, without latin descr. or type, 1997
• Frailea pygmaea var. gloriosa K.H. Prestlé
• Gattung Frailea (Br. & R.) Prestlé: 79, without latin descr. or type., 1997
• Frailea pygmaea var. grandiflora
• Frailea pygmaea var. insignia K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 91, without latin descr. or type, 1997
• Frailea pygmaea var. krausiana K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 80, without latin descr. or type, 1997
• Frailea pygmaea var. largoensis K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 77, without latin descr. or type, 1997
• Frailea pygmaea var. lilalunula
• Frailea pygmaea var. longispina F. Ritter
  Kakteen in Südamerika, 1: 204, 1979
• Frailea pygmaea var. maior F. Ritter
  Kakteen in Südamerika, 1: 204, 1979
• Frailea pygmaea var. major
  (Zaadlijst 2006 CaVe)
• Frailea pygmaea var. minanensis
• Frailea pygmaea var. mollispina-brunnea K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 99, without latin descr. or type, 1997
• Frailea pygmaea var. montana K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 81, without latin descr. or type, 1997
• Frailea pygmaea var. olimarensis K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 82, without latin descr. or type, 1997
• Frailea pygmaea var. phaeodisca (Spegazzini) Y. Ito
  Cacti (Borg), 70. 1952, 1952
• Frailea pygmaea var. planicosta F. Ritter
  Kakteen in Südamerika, 1: 204, 1979
• Frailea pygmaea var. pulcherrima (Arechavaleta) K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 84: 1997
• Frailea pygmaea var. sakusiana
• Frailea pygmaea var. salascana
• Frailea pygmaea var. salusiana
• Frailea pygmaea var. santanaensis K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 87, without latin descr. or type, 1997
• Frailea pygmaea var. viridilunula K.H. Prestlé
  Gattung Frailea (Br. & R.) Prestlé: 97, without latin descr. or type, 1997