Origin and Habitat: West & South West USA (Texas) and Mexico (Coahuila, Nuevo Leon, Tamaulipas)
Locus typicus: USA: Texas, near the Rio Grande.
Altitude range: From low elevations up to 1,150 metres above sea level.
Habitat and Ecology: The species grows in xerophyllous scrub in alluvial soils. This species prefers to clamber through woody vegetation for support of its slender, drab stems. It occurs in sandy soils of valleys and hills in semidesert brushlands. This species is widely used locally, but it is still abundant and widespread and not declining at a rate sufficient to qualify for a threatened category.

• Echinocereus poselgeri Lem.
• Cereus poselgeri (Lem.) J.M.Coult.
• Echinocereus poselgeri Small
• Wilcoxia poselgeri (Lem.) Britton & Rose

• Echinocereus poselgeri Lem.
• Cereus poselgeri (Lem.) J.M.Coult.
• Echinocereus poselgeri Small
• Wilcoxia poselgeri (Lem.) Britton & Rose
• Echinocereus kroenleinii (Mich.Lange) W.Blum & Waldeis
• Echinocereus poselgeri subs. kroenleinii Mich.Lange
• Wilcoxia kroenleinii A.Cartier
• Echinocereus poselgeri f. cristata hort.
• Wilcoxia poselgeri f. cristata hort.
• Echinocereus tamaulipensis (Werderm.) Mich.Lange
• Wilcoxia tamaulipensis Werderm.
• Echinocereus tamaulipensis subs. deherdtii Mich.Lange
• Echinocereus tamaulipensis subs. dehardii Mich.Lange
• Echinocereus tuberosus Poselg. in Rümpler
• Cereus tuberosus Poselg. non Pfeiff.
• Wilcoxia tuberosa (Poselg.) Kreuz.
• Echinocereus waldeisii Haugg
• Echinocereus tamaulipensis subs. waldeisii (Haugg) Mich.Lange

Description: Shrubby, scarcely branched, initially erect, later sprawling or clambering.
Stem: Very tall and slender, dark coloured up to 1.2 m long and 2 cm in diameter.
Ribs: 6-10.
Spines: Tan-greyish white; 1 central up to 9 mm long, enlarged at its base, 4mm long; 8-15 straight radials, 4,5mm long, closely appressed (except at the stem tip)
Roots: Tuberlike, contrarily to Echinocereus kroenleinii, the underground storage organ similar to dahlia tubers is not capable of producing new shoots. Those sprout out only from the main cut stem. Each plant can have up to 8 tubers, 10-20 mm in diameter, with a length of 60-100 mm. The colour is light brown in youth, later dark brown.
Flower: Pink Rose/Mauve Magenta (Pink-Purple).
Fruits: Ovoidal 20 mm Long, 10-15 mm Ø, dark green to brownish, pulp white
Seeds: Black 1,5 mm.
Blooming season: Late Spring/Early Summer.
Remarks: It apparently looks like some Peniocereus species. However the flowers, fruits, and seeds of Echinocereus poselgeri are characteristic for Echinocereus, somewhat comparable to those of Echinocereus reichenbachi.

Bibliography: Major references and further lectures
1) Corral-Díaz, R., Goettsch, B.K., Gómez-Hinostrosa, C., Terry, M. & Heil, K. 2013. Echinocereus poselgeri. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 25 May 2015.
2) Taylor, N.P. (1985): “The Genus Echinocereus”, A Kew Magazine Monograph: 64. Collingridge Books
3) Edward F. Anderson: The Cactus Family. Timber Press, Portland (Oregon) 2001
4) 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
5) David R Hunt; Nigel P Taylor; Graham Charles; International Cactaceae Systematics Group. "The New Cactus Lexicon" dh books, 2006

Cultivation and Propagation: Do not over water. They need to be kept in a cool, dry place during winter rest (at -5 +10°C). This is important for the flowers as well as for their health. Without this cool winter period they normally won't get any buds. It is quite frost hardy -7 (-10)° C.
Sun Exposure: Best in full or partial sun exposure. In mild climate they grow well when planted freely outside in well-drained soil.
Traditional uses and Trade: The species is found in Mexican trade, and the root is used locally as veterinary medicine (broken bones) and considered an anti-inflammatory. It is used as an ornamental.
Propagation: Seeds (usually), it also can be grown from cuttings, as it can branch with time.