Strombocactus

The genus and names in the literature

Plants of the World Online accepts Strombocactus disciformis and S. corregidorae. The first species includes subspecies disciformis and esperanzae. Britton and Rose published the genus in 1922. The former description as a single-species genus refers to the treatment before recognition of S. corregidorae. [2-WWW] [2-WWW] [Arias and Sánchez-Martínez 2010, POWO, as of 11 October 2026. Arias and Sánchez-Martínez, pp. 619–620]

In 2021, Bárcenas and colleagues proposed removing S. corregidorae to the genus Chichimecactus. Analysis of three chloroplast DNA regions, comprising 46 terminal tree units, indicated a different position for this species relative to S. disciformis. POWO currently retains both species in Strombocactus and treats Chichimecactus corregidorae as a synonym. The latter name therefore indicates a different classification of the same taxon. [Bárcenas et al. 2021, Bárcenas et al., abstract. POWO, as of 11 October 2026] [2-WWW]

Stem, tubercles and spination

Tubercles overlap, forming spiral rows with a scale-like appearance. Stems may be flattened, spherical, broad above and narrowed at the base, or elongated. In S. disciformis, thin, flexible spines fall off over time. S. corregidorae retains much longer, thicker spines over a large part of the stem. Body size and spine persistence help distinguish the species. [Arias and Sánchez-Martínez 2010, p. 619–621, tabela 1]

The description of S. corregidorae includes fibrous, superficial roots spreading sideways, slightly thickened near the stem. A strong napiform root was described in S. disciformis. The difference concerns underground organs, so the description of one species does not encompass the structure of the whole genus. [Arias and Sánchez-Martínez 2010, Arias and Sánchez-Martínez, p. 620. Ivannikov et al., p. 2] [Ivannikov et al. 2022, Arias and Sánchez-Martínez, p. 620. Ivannikov et al., p. 2]

Skalne siedliska

Natural sites form a canyon system in Querétaro, Hidalgo and Guanajuato. Plants root in fissures containing fine soil material, on steep slopes and almost vertical walls with calcareous shale. Surroundings may be almost unvegetated, while some individuals grow beside sheltering shrubs. Individual microhabitats therefore include both exposed rock and local shelter. [Camacho-Velázquez et al. 2018, p. 89–90]

In the 2014–2017 seed-development study, material of S. corregidorae and the nominate subspecies of S. disciformis came from single localities in Querétaro. Material of subsp. esperanzae was obtained from botanical garden collections because the authors did not find it at the natural site checked. The scope of this observation concerns a specific field search. [Camacho-Velázquez et al. 2018, p. 90, sekcja 2.1]

Flowers and nectar secretion

Flowers develop in the upper stem and open during the day. They are funnel-shaped. The perianth is white or yellowish white in nominate S. disciformis, intense magenta in subsp. esperanzae and yellow in S. corregidorae. In all three taxa studied, the nectary forms a ring around the style base, below attachment of the deepest stamens. Secretion emerges through modified stomata called nectarostomata. [Camacho-Velázquez et al. 2019, p. 101–104, ryc. 1–3]

Flower arrangement, daytime opening and the presence of pollen and nectar support the hypothesis of bee pollination. The anatomical study did not measure visit effectiveness. Secretory tissue structure and nectar measurement are explained in the article on Strombocactus nectaries and pollination. [Camacho-Velázquez et al. 2019, p. 106–107]

Tiny seeds and the beginning of a seedling

In the comparative study, seeds of all three taxa had mean lengths below 0.5 mm without the additional aril. In both subspecies of S. disciformis, the aril develops from the funiculus, which joins the ovule to the placenta. Its tissue contains extensive air spaces. S. corregidorae develops seeds lacking this structure. All three taxa floated on the water surface in the laboratory experiment. [Camacho-Velázquez et al. 2018, p. 91–94, ryc. 2–7]

On moist filter paper, at 25°C with a twelve-hour photoperiod, mean germination was 92.08–97.08%, depending on the taxon. Eight replicates of 30 seeds were used for each. This result documents the germination capacity of specific batches. The next stage involves maintaining a small seedling in its microhabitat. The full description of development and experimental conditions is in the article on seed arils, floating and germination. [Camacho-Velázquez et al. 2018, p. 91, 94–95, 100]

Propagation and protecting collections

Laboratory data indicate that, in the batches studied, sowing can yield numerous seedlings without cutting or abrading the coat. A separate experiment on S. disciformis demonstrated regeneration of new shoots from young-plant fragments in vitro. This procedure was not tested on S. corregidorae, and the authors did not identify the subspecies of the S. disciformis material. Sowing and tissue regeneration are distinct, documented propagation routes. [Camacho-Velázquez et al. 2018, Camacho-Velázquez et al., pp. 91, 100. Ivannikov et al., pp. 2–4] [Ivannikov et al. 2022, Camacho-Velázquez et al., pp. 91, 100. Ivannikov et al., pp. 2–4]

A study of sale advertisements from 2014–2015 revealed widespread circulation of seeds and plants under several Strombocactus taxon names. Some sellers gave natural localities of origin. The account shows collector pressure on plants with restricted ranges and the importance of documented propagation collections. Its results describe the historical state of the offers studied. [Olmos-Lau and Mandujano 2016, pp. 3–7]

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