: Jujuy and Salta Provinces, Northern Argentina (Los Andes).
Altitude: From 3500 to 4200 metres above sea level.
Habitat: It is found in high, dry, rocky grasslands in valleys and rocky slopes of the Andes in fully exposed sites along with a succulent flora comprising Lobivia chrysanthaSN|4674]]SN|4674]], Gymnocalicium spegazzinii, Pyrrocactus umadeave. Inhabitants must be very rugged in order to tolerate such extremes in exposure. Echinopsis korethroidesSN|2757]]SN|2757]] is such a robust individual. However in habitat the plant is often bathed in fog during the summer months and even when exposed to full sun, heat is typically not a factor. The dense covering of spines reduces the interception of solar radiation by the stem surface lowering the risks of overheating the apex during a summer day and of freezing during a winter night.

• Echinopsis formosa subs. korethroides (Werderm.) M.Lowry
• Echinopsis korethroides Werderm.
• Eriosyce korethroides (Werderm.) Backeb. in Backeb. & F.M.Knuth
• Lobivia korethroides (Werderm.) Werderm.
• Soehrensia korethroides (Werderm.) Backeb.
• Trichocereus korethroides (Werderm.) H.P.Kelsey & Dayton

• Echinopsis formosa subs. korethroides (Werderm.) M.Lowry
• Echinopsis korethroides Werderm.
• Eriosyce korethroides (Werderm.) Backeb. in Backeb. & F.M.Knuth
• Lobivia korethroides (Werderm.) Werderm.
• Soehrensia korethroides (Werderm.) Backeb.
• Trichocereus korethroides (Werderm.) H.P.Kelsey & Dayton

• Echinopsis formosa (Pfeiff.) Jacobi ex Salm-Dyck
• Acanthocalycium formosum (hort. ex Pfeiff.) Backeb.
• Cereus gilliesii F.A.C.Weber in Bois
• Echinocactus formosus Pfeiff.
• Echinonyctanthus formosus Lawr.
• Lobivia formosa (Pfeiff.) Dodds
• Soehrensia formosa (Pfeiff.) Backeb.
• Trichocereus formosus (Pfeiff.) F.Ritter
• Echinopsis formosa subs. kieslingii (Rausch) M.Lowry
• Echinopsis kieslingii (Rausch) Anceschi & Magli
• Lobivia kieslingii Rausch
• Echinopsis formosa var. maxima (Backeb.)
• Soehrensia formosa var. maxima Backeb.
• Echinopsis formosa var. pinchasensis (Rausch)
• Lobivia formosa var. pinchasensis Rausch
• Echinopsis formosa var. polycephala (Backeb.)
• Soehrensia formosa var. polycephala Backeb.
• Echinopsis formosa subs. rosarioana (Rausch) M.Lowry
• Lobivia formosa var. rosarioana (Rausch) Rausch
• Lobivia rosarioana Rausch
• Echinopsis oreopogon (Speg.) Werderm.
• Acanthocalycium oreopogon (Werderm. ex Speg.) Backeb. in Backeb. & F.M.Knuth
• Lobivia oreopepon Speg.
• Lobivia oreopogon Werderm. in Backeb. & Werderm.
• Soehrensia oreopepon (Speg.) Backeb.
• Echinopsis uebelmanniana (Lembcke & Backeb.) A.E.Hoffm.
• Lobivia formosa var. uebelmanniana (Lembcke & Backeb.) Rausch
• Soehrensia uebelmanniana Lembcke & Lembcke
• Trichocereus uebelmannianus (Lembcke & Lembcke) F.Ritter

• Echinopsis formosa var. albispina F.A.C.Weber ex Schelle
• Acanthocalycium formosanum var. albispinum (F.A.C.Weber ex Schelle) Y.Itô

• Echinopsis formosa subs. randallii (Cárdenas) M.Lowry
• Echinopsis randallii (Cárdenas) H.Friedrich & G.D.Rowley
• Helianthocereus randallii (Cárdenas) Backeb.
• Lobivia formosa var. randallii (Cárdenas) Rausch
• Trichocereus randallii Cárdenas

: Echinopsis korethroidesSN|48]]SN|2757]] is probably one of the many geographical forms of the extremely variable Echinopsis formosaSN|2757]]SN|48]] and is placed as a subspecies by some authorities. It is a massive growing barrel cactus with a solid and spiny presence, solitary at first, but often branching basally to form colonies later. The dense yellowish-brown or reddish-brown spines would protect it from the extremes of cold and sunshine. The new spines are actually dark brown and appear in the spring.
The spines can become so dense on mature specimens that the plant's body becomes obscured from view.
Stem: Globose, oblong to shortly columnar, flat and somewhat depressed at the top, up to 70 cm high and 30-50 cm wide, multiply- ribbed, dull to glossy pale green, up to 0,5-1(-2) m tall, 20-35(-50) cm in diameter.
Ribs: More than 20, narrow, tuberculate
Areoles: whitish.
Radial spines: 12-20, needle-like, spreading, straight or slightly curved, colourful dry grass (or straw), amber, brown or reddish brown with dark tips, turning greyish-white as they ages, unequal, up to 3 (or more) cm long
Central spines: 4 , acicular, yellowish to reddish-brown, sometimes banded and flattened, sharp, of variable length which, in some cases, can reach the 20 cm.
Flowers: Diurnal, orange, pink, red to dark purple, bell-shaped or funnelform, originating in the apical zone and are about 7 cm long and 4,5 cm broad. Tube short. axils of scales filled with woolly hairs.
Blooming period: Open in the day in the spring.

: 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) N. L. Britton, J. N. Rose “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Volume 4, The Carnegie Institution of Washington, Washington 1923
5) Curt Backeberg “Die Cactaceae: Handbuch der Kakteenkunde” Gustav Fischer Verlag, Stuttgart New York 1982–1985
6) John Borg “Cacti: a gardener's handbook for their identification and cultivation” Blandford P., 1970
7) George Gilbert Green “Cacti and succulents” Pitman Pub. Corp., 1953
8) Hecht, “BLV Handbuch der Kakteen” BLV Verlagsgesellschaft mbH, München
9) Erik Haustein “Der Kosmos-Kakteenführer” Balogh Scientific Books 1998
10) Arthur Gibson, Park Nobel “The cactus primer” Harvard University Press, 01/Oct/1990

: Echinopsis korethroidesSN|2757]]SN|2757]] is one of the more cold hardy barrel cacti, that tolerates
in winter both, ice, snow, hail, and rain and temperatures down to – 12° C
Growth rate: It is a relatively rapidly growing species that will make clumps given the best conditions.
Soils: It likes very porous standard cactus mix soil. Prefer a low pH compost, avoid substrata rich in limestone; otherwise growth will stop altogether.
Repotting: This plant needs plenty of space for its roots, repotting should be done every other year or when the it has outgrown its pot. Use pot with good drainage.
Watering: Needs moderate to copious waterings in summer, but do not overwater (Rot prone), keep dry in winter at a minimum temperature of 0°C.
Fertilization: Feed with a high potassium fertilizer in summer.
Hardiness: Reputedly resistant to frost if kept on the dry side prior to, and during, cold weather (hardy to -12 C ° C, or less for short periods). Zone 8b to 10
Exposition: The plant tolerates extremely bright situations which encourages flowering and heavy spine production, but is likely to suffer from sun scorch or stunted growth if over exposed to direct sunlight during the hottest part of the day in summer. It may tolerate filtered sunlight or afternoon shade.
Uses: It is an excellent plant for container growing. It always looks good and stays small. It look fine in a cold greenhouse and frame or outdoor in a rockery.
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 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: This species is particularly easy and accommodating, seldom suffer of cryptogamic diseases. Rot it is only a minor problem with gymnocalyciums if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much.
Propagation: Division of larger clumps, direct sow after last frost. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants! To make a cutting twist off a branch and permit it to dry out a couple of weeks, lay it on the soil and insert the stem end partially into the soil. Try to keep the cutting somewhat upright so that the roots are able to grow downward.