Origin and Habitat: Frailea pygmaeaSN|3317]]SN|3317]] is marginally distributed in Argentina (Entre Ríos) and Brazil (Rio Grande do Sul), and in all of Uruguay.
Altitude: This species occurs at elevations between 0 and 400 metres above sea level.
Habitat and Ecology: Frailea pygmaeaSN|3317]]SN|3317]] usually grows 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 sparsely distributed, but abundant in some areas where it is found. It grows on rocky outcrops and stony fields in pampa grasslands, a habitat that has a very high potential to be used for agriculture, often in association with other cacti like Notocactus ottonisSN|15901]]SN|751]], Notocactus scopaSN|751]]SN|15901]] v. xicoi and Wigginsia sp. The major threats to this species are grazing and cattle trampling, agriculture, forestry of Eucalyptus, invasive grasses and fire.

• Frailea pygmaea (Speg.) Britton & Rose
• Astrophytum pygmaeum (Speg.) Halda & Malina

• Frailea pygmaea (Speg.) Britton & Rose
• Astrophytum pygmaeum (Speg.) Halda & Malina
• Frailea pygmaea var. aceguaensis Prestlé
• Frailea pygmaea var. albispina
• Frailea pygmaea subs. altigibbera (F.Ritter) P.J.Braun & Esteves
• Frailea pygmaea var. altigibbera F.Ritter
• Frailea pygmaea var. applanata Prestlé
• Frailea pygmaea var. argenta Prestlé
• Frailea pygmaea subs. asperispina (F.Ritter) P.J.Braun & Esteves
• Astrophytum asperispinum (F.Ritter) Halda & Malina
• Frailea asperispina F.Ritter
• Frailea pygmaea var. atrofusca Backeb.
• Frailea pygmaea subs. aureinitens (Buining & Bredero) P.J.Braun & Esteves
• Astrophytum aureinitens (Buining & Bredero) Halda & Malina
• Frailea aureinitens Buining & Bredero
• Frailea pygmaea subs. aureispina (F.Ritter) P.J.Braun & Esteves
• Astrophytum aureispinum (F.Ritter) Halda & Malina
• Frailea aureispina F.Ritter
• Frailea pygmaea var. auricantha Prestlé
• Frailea pygmaea var. bagensis Prestlé
• Frailea pygmaea var. brunneo-mollispina hort.
• Frailea pygmaea var. cabucaensis Prestlé
• Frailea pygmaea var. carpinteria Prestlé
• Frailea pygmaea var. castaneoidea Prestlé
• Frailea pygmaea var. catiensis
• Frailea pygmaea var. corallina Prestlé
• Frailea pygmaea var. curvispina F.Ritter
• Frailea pygmaea var. dadakii (Frič ex A.Berger) Backeb.
• Astrophytum dadakii (Frič ex A.Berger) Halda & Malina
• Echinocactus dadakii Frič ex A.Berger
• Frailea dadakii Frič ex A.Berger
• Frailea oreopygmaea var. dadakii (Frič ex A.Berger) Prestlé
• Frailea pygmaea var. elegantissima
• Frailea pygmaea var. gemmrichii Prestlé
• Frailea pygmaea var. gloriosa Prestlé
• Frailea pygmaea var. grandiflora
• Frailea pygmaea subs. hyssooniana Prestlé
• Frailea pygmaea var. insignia Prestlé
• Frailea pygmaea var. krausiana Prestlé
• Frailea pygmaea var. largoensis Prestlé
• Frailea pygmaea subs. lilalunula (F.Ritter) P.J.Braun & Esteves
• Frailea pygmaea var. lilalunula F.Ritter
• Frailea pygmaea var. longispina F.Ritter
• Frailea pygmaea var. maior F.Ritter
• Frailea pygmaea var. minanensis
• Frailea pygmaea var. mollispina-brunnea Prestlé
• Frailea pygmaea var. montana Prestlé
• Frailea pygmaea var. olimarensis Prestlé
• Frailea pygmaea var. planicosta F.Ritter
• Frailea pygmaea var. pulcherrima (Arechav.) Prestlé
• Astrophytum pulcherrimum (Arechav.) Halda & Malina
• Echinocactus pulcherrimus Arechav.
• Frailea pulcherrima Speg.
• Malacocarpus pulcherrimus Britton & Rose
• Frailea pygmaea var. sakusiana
• Frailea pygmaea var. salascana
• Frailea pygmaea var. salusiana
• Frailea pygmaea var. santanaensis Prestlé
• Frailea pygmaea var. viridilunula Prestlé

• Frailea pygmaea subs. albicolumnaris (F.Ritter) Hofacker
• Astrophytum albicolumnare (F.Ritter) Halda & Malina
• Frailea albicolumnaris F.Ritter

• Frailea pygmaea var. aurea (Backeb.) Backeb.
• Astrophytum aureum (Backeb.) Halda & Malina
• Frailea aurea Backeb.
• Frailea oreopygmaea var. aurea (Backeb.) Prestlé

• Frailea pygmaea subs. fulviseta (Buining & Bredero) P.J.Braun & Esteves
• Astrophytum fulvisetum (Buining & Bredero) Halda & Malina
• Frailea fulviseta Buining & Bredero

Description: Frailea pygmaeaSN|3317]]SN|3317]] 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.
Notes Frailea pygmaeaSN|3317]]SN|3317]] 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 invalid and nowadays considered as synonyms.
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.

Bibliography: Major references and further lectures
1) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
2) James Cullen, Sabina G. Knees, H. Suzanne Cubey "The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass" Cambridge University Press, 11/Aug/2011
3) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
4) Marlon C Machado. “Fascinating Frailea, Part 1: General impressions.” Cactus World (BCSS) Volume 25 No. 1 March 2007
5) Marlon C Machado.”Fascinating Frailea, Part 2: Review of the species from Rio Grande do Sul.” Cactus World (BCSS) Volume 25 No. 2 June 2007
6) Larocca, J., Machado, M. & Duarte, W. 2013. Frailea pygmaea. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 15 February 2014.

Cultivation and Propagation: Frailea pygmaeaSN|3317]]SN|3317]] is a summer grower species relatively easy to grow. Characteristically, during the dry season plants retract completely under the ground both in the wild and in cultivation too.
Growth rate: Fraileas are relatively short-lived plants, only lasting few years (rarely more than 10-15 years in cultivation) and, possible annuals in habitat! In fact they reseed readily around the base of the mother plant from self-set seed if kept reasonably moist during warm weather. It is a good idea to keep restarting them from seed; what looks like a healthy big plant may suddenly die of old age without warning.
Soil: Use mineral well permeable substratum with little organic matter (peat, humus), plants may become too elongated if compost is too rich.
Repotting: Re-pot every 2 years. Use pot with good drainage.
Fertilization: It grows much faster with a low nitrogen content fertilizer in spring and summer. Potassium helps maintaining the plants compact and healthy.
Watering: Requires careful watering to keep plant compact. Water sparingly from March till October, the thin, fibrous roots suffer if there is humidity, therefore the plant should be watered only when the surrounding terrain is dry. Keep dry as soon as the temperature starts dropping in October and keep it perfectly dry in winter at temperatures from 5 to 15 degrees centigrade.
Hardiness: They need a minimum temperature of 5-10° C (but occasionally temperatures of a few degrees below 0° are not dangerous if kept on the dry side prior to, and during, cold weather). It tends to rot in winter during the resting phase, if kept wet. In the rest period no high atmospheric humidity!!
Sun Exposure: Light shade to full sun, its colour tends to richer and darker when grown in light shade. In a shaded position the plants grow faster, but are not flat shaped and dark coloured.
Uses: It is an excellent plant for container growing. It always looks good and stays small.
Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for:
- Red spiders: Red spiders may be effectively rubbed up by watering the infested plants from above.
- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects.
- Scales: Scales are rarely a problem.
- Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much. To prevent rottenness it is also advisable to surround its root neck by very rough sand or grit, this help a fast water drainage.
Propagation: With fresh harvested seeds or (rarely) by grafting. Fraileas set seed (when well grown) and grow easily from seed. In fact, they are reported to set seed even if the flower doesn’t open. This self-fertilization is called cleistogamy. Seedlings dislike strong light and dry conditions and need to be repotted frequently during the first few years. However, old plants become senile and have a tendency to succumb to disease and a weak root system. At this stage, as is well known, they die suddenly. So, after they reach about 4-5 cm in diameter grow them slowly, and adopt a new repotting period, using intervals of every 3-4 years. Additionally grow them under drier conditions or with stronger sunlight. But plants are sometine grafted to accelerate growth, but the grafted plants are typical rather tall growing, compared with plants on their own roots that are usually more flat to the ground.