Origin and Habitat: This cactus is endemic to Brazil, where it occurs in Bahia, Piauí, Pernambuco, Minas Gerais and Goias.
Type locality: Riacho de Santana, Bahia, Brazil
Altitude range: 220 to 1,200 metres above sea level.
Habitat and Ecology: Arrojadoa rhodanthaSN|4866]]SN|4847]] can be found in very arid areas in the underwood of the Caatinga on various substrates (including the shade of dense caatinga forest and in the open on inselbergs), and entering the caatinga/campo rupestre ecotone. In the same area the following cactus species can also be found: Arrojadoa penicillataSN|4847]]SN|4866]], Cereus jamacaruSN|8073]]SN|6995]], ColeocepbaloCereus goebelianusSN|6995]], Melocactus salvadorensisSN|26074]]SN|26074]] and Tacinga inamoenaSN|19087]]SN|19087]]. This species is widespread and common throughout its range. The subpopulations have suffered from declines due to habitat loss. The habitat is under degradation due to deforestation for logging and for agriculture, cattle ranching, urbanization, quarrying, as well as due to fires.

• Arrojadoa rhodantha subs. reflexa P.J.Braun

• Arrojadoa rhodantha Britton & Rose
• Arrojadoa horstiana P.J.Braun & Heimen
• Cephalocereus rhodanthus Werderm.
• Cereus rhodanthus Gürke
• Arrojadoa rhodantha var. occibahiensis P.J.Braun
• Arrojadoa rhodantha var. theunisseniana (Buining & Bredero) P.J.Braun
• Arrojadoa theunisseniana Buining & Bredero in Krainz

• Arrojadoa rhodantha var. anguinea (P.J.Braun & Esteves) P.J.Braun & Esteves
• Arrojadoa aureispina var. anguinea P.J.Braun & Esteves

• Arrojadoa rhodantha subs. aureispina (Buining & Bredero) P.J.Braun & Esteves
• Arrojadoa aureispina Buining & Bredero

• Arrojadoa rhodantha subs. canudosensis (Buining & Bredero) P.J.Braun
• Arrojadoa canudosensis Buining & Bredero

• Arrojadoa rhodantha var. guanambensis (P.J.Braun & Heimen) P.J.Braun & Esteves
• Arrojadoa aureispina var. guanambensis P.J.Braun & Heimen

Description: Arrojadoa rhodanthaSN|4847]]SN|4847]] is a shrubby cactus, at first erect, afterwards branching basally, and clambering that can reach a height of over one metre. Every year the tubulaar violet-red flowers are produced in clusters from a cephalium at the tops of the joints.
Stems: Joined 1 to 2 meters long. Joints short cylindric, flattened at the top, dark green 20-40(-50) mm thick.
Roots: Fibrous.
Ribs: Ten to twelve, fairly shallow.
Areoles: Small, with short wool, in close proximity, usually less than 1 cm apart.
Spines: At first brown, in age white when young accompanied by some long cobwebby hairs.
Central spines: 5-6, similar to the radials except a little longer and stouter to 3 cm long.
Radial spines: About 20, to 12 mm long.
Pseudocephalia (flower bearing structures): At the tops of the joints with 1 .5-2 cm long brown wool and up to 3 cm long reddish brown bristles.
Flowers: Deep pink to violet-red, diurnal at the upper areoles, forming in clusters of 12 to 14 in a pseudocephalium at the tops of branches, 3 to 4 cm long, 1.2-2(-3) cm in diameter, nearly cylindric, the tube short pink, rigid, ovary and lower part of tube naked. Perianth-segments in several rows, short, erect, uppermost scales and perianth-segments similar, obtuse. Stamens numerous, included.
Fruits (berries): Red, naked, juicy oblong to obovate, about 2 cm long.
Seeds: Small, black.

Bibliography: Major references and further lectures
1) Machado, M., Braun, P., Taylor, N.P. & Zappi, D. 2013. Arrojadoa rhodantha. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 16 August 2014.
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) N. L. Britton, J. N. Rose: “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume 2, The Carnegie Institution of Washington, Washington 1920
6) Haustein, Erik “Der Kosmos-Kakteenführer” Franckh-Kosmos 1983
7) Cullmann W., Götz E., Gröner G.”Kakteen: Kultur, Vermehrung und Pflege - Lexikon der Gattungen und Arten” Ulmer, Stuttgart, 1984
8) Willy Cullmann, Erich Götz (Dozent Dr.), Gerhard Gröner “The encyclopedia of cacti” Timber Press, 1987
9) Clive Innes “Complete Handbook of Cacti and Succulents” Van Nostrand Reinhold Company, 01/Dec/1981
10) Urs Eggli, Leonard E. Newton: “Etymological Dictionary of Succulent Plant Names”. Springer, Berlin/Heidelberg 2010