Structure of the branched stems
The genus Armatocereus comprises cacti with cylindrical, ribbed stems. Successive segments connect at constrictions. Spines arise from areoles, and accounts distinguish central spines from the surrounding radial spines. Spine length and number, as well as floral structures, differ among species and subspecies. Keys designed for mature plants use these characters in combination. [Loaiza and Roque Gamarra 2016, pp. 37–38, pp. 1–2] [Rojas et al. 2026, pp. 37–38, pp. 1–2]
Current names and earlier identifications
POWO accepts seven Armatocereus species, distributed from Ecuador to Peru. Earlier names in publications sometimes refer to narrower circumscriptions than the current ones. Material called A. mataranus subsp. ancashensis falls within A. matucanensis, while A. brevispinus is treated as a subspecies of A. godingianus. Experimental details are assigned to the studied population and its original identification. [2-WWW] [2-WWW] [Rojas et al. 2026, POWO records 5208-1, 19747-2 and 1160479-2, 12 October 2026] [Loaiza and Roque Gamarra 2016, POWO records 5208-1, 19747-2 and 1160479-2, 12 October 2026]
Roots and DNA content
Two studies from 2026 describe different levels of plant organization. In A. laetus from Laipuna, flow in small roots was monitored for 17 months. In the ancashensis population from Cosma, chromosomes and nuclear DNA content were studied in seedlings and young stems. The first study revealed rapid use of small rainfall events. The second found a diploid complement of 22 chromosomes and endoreduplication in stem tissue. The species cards expand on the conditions and limits of inference specific to each study. [Rojas et al. 2026, pp. 3–6, 10–11, pp. 3–14] [Würzberg et al. 2026, pp. 3–6, 10–11, pp. 3–14]