Origin and Habitat: Uruguay and Brazil (Rio Grande do Sul). Parodia mueller-melchersiiSN|17641]]SN|17641]] has a small range and is not abundant.
Altitude: It occurs at elevations between 150 and 300 metres above sea level.
Habitat: Grassland or pampas in rocky areas (eg. inland cliffs, mountain peaks) It is threatened by land use change for Eucalyptus plantations and cattle ranching. Several subpopulations have already disappeared, and others continue to decline.

• Parodia mueller-melchersii (Backeb.) N.P.Taylor
• Notocactus mueller-melchersii Frič ex Backeb.
• Notocactus mueller-moelleri Frič ex Backeb. & F.M.Knuth
• Ritterocactus mueller-melchersii (Frič ex Backeb.) Doweld

• Parodia mueller-melchersii (Backeb.) N.P.Taylor
• Notocactus mueller-melchersii Frič ex Backeb.
• Notocactus mueller-moelleri Frič ex Backeb. & F.M.Knuth
• Ritterocactus mueller-melchersii (Frič ex Backeb.) Doweld
• Notocactus mueller-melchersii var. eugeniae (Vliet) N.Gerloff & Neduchal
• Notocactus eugeniae Vliet
• Parodia mammulosa subs. eugeniae (Vliet) Hofacker
• Ritterocactus mammulosus subs. eugeniae (Vliet) Doweld
• Notocactus rutilans f. robustior N.Gerloff
• Notocactus rutilans var. robustior N.Gerloff
• Notocactus rutilans var. roseiflorus (H.Schloss. & Bredero) N.Gerloff & Neduchal
• Notocactus roseiflorus H.Schloss. & Bredero
• Parodia rutilans (Däniker & Krainz) N.P.Taylor
• Notocactus rutilans Däniker & Krainz
• Ritterocactus rutilans (Däniker & Krainz) Doweld
• Parodia rutilans subs. veeniana (Vliet) Hofacker
• Notocactus mueller-melchersii var. veenianus (Vliet) N.Gerloff & Neduchal
• Notocactus veenianus Vliet
• Ritterocactus rutilans subs. veenianus (Vliet) Doweld

• Parodia mueller-melchersii subs. gutierrezii (W.R.Abraham) Hofacker
• Notocactus gutierrezii W.R.Abraham
• Notocactus rutilans var. gutierrezii (W.R.Abraham) N.Gerloff & Neduchal
• Ritterocactus mueller-melchersii subs. gutierrezii (W.R.Abraham) Doweld

• Parodia mueller-melchersii subs. winkleri (Vliet) Hofacker
• Notocactus mueller-melchersii var. winkleri (Vliet) N.Gerloff & Neduchal
• Notocactus winkleri Vliet
• Ritterocactus mueller-melchersii subs. winkleri (Frič ex Backeb.) Doweld

Description: Parodia mueller-melchersiiSN|17641]]SN|17641]] (best known as Notocactus mueller-melchersiiSN|17642]]SN|17642]]) in contrast to most notocacti (that have almost always yellow flowers), has flowers ranging from creamy yellow to lavender. The spines are also variable ranging from yellowish-white to dark red-brown. Several of its colour and morphological variant was early classified as different independent varieties, but nowadays all this plant are considered part of a multiform species, where each variant form is linked to others by populations of plants with intermediate characteristics.
Habit: It is a perennial stem succulent. Plants usually solitary. Multiple branches may also been produced when the apex is damaged.
Stem: Globose to shortly columnar , dull green, to 8-10(-24) cm tall and 5-6 cm in diameter or slightly larger. Crown wooly and spiny.
Ribs: (18-)20-24, vertical or weakly spiralling, not distinctly tuberculate with chin-like humps below the areoles more evident near stem apex.
Areoles: Initially white felted .
Central spines: 1-3, straight, pointing to side or downward, 7-20 mm long straight, not flattened, stiff , horn coloured, yellowish, light brown, reddish brown or dark red with dark spots. The spine-bases are red-brown and tips are often darker.
Radial spines: 12-18, or more, slender, needle-like, diverging, pale yellow or whitish, darker-tipped 5-8 mm long.
Flowers: Several produced together around the stems apex, creamy yellow, citron yellow, pink, light lavender or reddish becoming paler to yellowish in the throat or pale golden yellow, to 3-4 cm long and 5-6 cm in diameter; pericarpels and floral tubes with white wool and dark bristles. Stigma pale carmine.
Blooming season: Summer.
Fruits: Club shaped elongating at base, 1,5 cm long thin-walled.

Bibliography: Major references and further lectures
1) Tony Mace “Notocactus: a review of the genus incorporating Brasilicactus, Eriocactus and Wigginsia” Editorial Board/National Cactus & Succulent Society, 1975
2) Edward Anderson “The Cactus family” Timber Press, Incorporated, 2001
3) 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
4) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006
5) Larocca, J., Machado, M. & Duarte, W. 2013. Parodia mueller-melchersii. In: IUCN 2013. "IUCN Red List of Threatened Species." Version 2013.1. <www.iucnredlist.org>. Downloaded on 28 October 2013.
6) H. Krainz “Die Kakteen: eine Gesamtdarstellung der eingeführten Arten nebst Anzucht- und Pflege-Anweisungen,” Parts 1-16” Franck, 1956
7) Hans Hecht “BLV-Handbuch der Kakteen” BLV-Verlagsgesellschaft, 1982
8) Haustein, Erik. “Der Kosmos-Kakteenführer.” Kosmos / Gesellschaft der Naturfreunde., Stuttgart, 1983
10) Walther Haage "Kakteen von A bis Z", Quelle & Meyer Verlag: Heidelberg, 1986
11) Willy Cullman, Erich Gotz, Gerhard Groner “The Encyclopedia of Cacti” Alphabooks, 1986

Cultivation and Propagation: It is easy to grow. It prefers a neutral to slightly acidic mineral-based potting mix with a good drainage. It likes a warm bright location, does great in partial shade but doesn't like full, hot blazing sun in the central summer month. Can support quite some water during the growing season but pot plants in winter are wet-sensitive and needs to be kept dry (rots easily if soil is wet and cold) tends to lose its roots in winter. Usually it is recommended to over-winter this plant in a bright and warm greenhouse with at least 8-10° C, but it has proved to tolerate temperatures as low as -5° C for short periods.
Propagation: Seeds, cuttings or root suckers (if available). Not too difficult to raise from seed.