Name, range and sites studied in Chihuahua
Homalocephala parryi (formerly Echinocactus parryi, also Emorycactus parryi) is the name accepted in POWO. The database places its natural range in northern Mexico, in Sonora, Chihuahua and Coahuila. The latest propagation studies describe selected populations from Chihuahua. Their results refer to local material within the more broadly defined botanical range. [2-WWW] [Vargas-Luna et al. 2026]
The account from 2026 described sites on hills of sedimentary and metamorphic rock, usually at 1200–1300 m above sea level, among grassy vegetation and dry scrub. Plants at higher elevations in the Sierra de Samalayuca were also recorded. Seeds for the experiment came from one small population in Ahumada municipality. The authors identify settlement expansion and collection of wild specimens as factors transforming local sites. [Vargas-Luna et al. 2026]
Stem, spines and ripening fruit
The adult stem is usually solitary, globular to shortly cylindrical. The description compiled in the study from 2026 gives 15–45 cm in height and 15–30 cm in diameter, with usually 13 sharp ribs. Four strong central spines can reach 4–6 cm long and curve away from the areole. Their surfaces are covered with greyish hairs. Reddish colour is especially pronounced on young spines and after older ones are wetted. The yellow flowers have a reddish perianth base and are about 5–7 cm in diameter. [Vargas-Luna et al. 2026]
The young fruit is green and fleshy. As it ripens, it turns brown and dries, retaining surface hairs that arise beside pointed scales. Seeds escape through an opening at its base. In material from Ahumada, fruits contained about 233 seeds on average. Each has a black, sculptured coat with a dorsal edge and a deeply set scar where it was attached to the ovule stalk. The curved embryo occupies most of the seed interior. [Vargas-Luna et al. 2026]
Jak siewka buduje pierwsze areole
Germination begins with water uptake, seed-coat rupture and emergence of the embryonic root. In the observed series, numerous transparent root hairs appeared within 10–20 days after sowing. The developing hypocotyl raised two pointed cotyledons, initially tightly pressed together. The main root began producing branches, increasing the area of contact with the substrate. [Vargas-Luna et al. 2026]
The first areole was observed about 30–40 days after sowing. It contained hairs and 4–6 delicate spines. Further areoles appeared after 50–60 days, when the first tubercle-like projections could be recognised on the stem. As growth continued, the cotyledons became increasingly difficult to distinguish from the rest of the stem. This account shows how a small seedling with two cotyledons develops into a plant with an areole-covered surface and an increasingly distinct rib arrangement. [Vargas-Luna et al. 2026]
Seed storage and preparation
Vargas-Luna et al. compared seeds collected from five fruits in 2021 and five fruits in 2022. Both lots were sown in June 2022 after storage for one year and one month respectively, at about 24°C in a very dry atmosphere. For each lot, treatments included an untreated control, soaking in water for 24 or 48 hours, and a treatment termed stratification by the authors, involving 20 days at 5°C. A total of 400 seeds were used, with five replicates of 10 per combination. [Vargas-Luna et al. 2026]
Sowing took place in a greenhouse, in containers with a 1:1 mixture of coconut fibre and tezontle, a porous volcanic material. During 50 days of observation, temperature ranged from 20 to 40°C. Preparation at 5°C gave the highest germination percentage, 44% in the year-old lot and 32% in the month-old lot. The corresponding controls germinated at 20% and 4%. These data describe treatment effectiveness in this greenhouse, with specified material and temperature range. [Vargas-Luna et al. 2026]
The authors link higher germination in the year-old lot with possible after-ripening and a change in seed dormancy. In this experiment, however, storage duration was linked to harvest year. Mother plants and seed development conditions could have differed between seasons. The result supports further trials of cooling and storage, while rigorous separation of these factors requires dividing the same seed lot among different storage periods. [Vargas-Luna et al. 2026]
| Partia nasion | Kontrola | 20 days at 5°C |
|---|---|---|
| 2022 harvest, stored for one month | 4% | 32% |
| 2021 harvest, stored for one year | 20% | 44% |
In vitro propagation and regulation of shoot development
In the study by García-González et al. from 2020, published under the name Echinocactus parryi, the starting material was seedlings obtained in sterile culture. Removing part of the seed coat accelerated the onset of germination. Rootless fragments of 40-day-old seedlings were then placed upside down on MS medium. Comparisons included mineral composition, pH, agar quantity, and combinations of the cytokinin BAP and auxin IAA, two regulators affecting cell division and the organisation of developing organs. [García-González et al. 2020]
The highest mean number of normally developed shoots, 2,9 per plant fragment after 120 days, was obtained with 2 mg/l BAP and 0,5 mg/l IAA, in one medium formulation at pH 8. Each combination was assessed on eight fragments. Many of the other formulations favoured callus formation, a mass of proliferating cells without a distinctly organised shoot. Increasing the regulator dose could therefore change the developmental pathway rather than increase the number of plants suitable for further cultivation. [García-González et al. 2020]
Rooting was carried out as a separate stage. Treatments included TIBA, a compound inhibiting directional auxin transport. The authors associated its action with reduced callus formation and root production. The proposed explanation involving the plant’s own auxins remains a hypothesis, since their tissue concentrations were not measured. Five months after rooted plants were transferred to the greenhouse, 58% of specimens survived. The transition from medium to substrate was therefore an important stage of the whole procedure. [García-González et al. 2020]
Care of young plants
The greenhouse seed experiment involved frequent irrigation during germination, followed after 50 days by gradual lengthening of intervals between waterings. Seedlings about 1 cm tall were moved to separate pots. This sequence separates maintenance of the moisture needed to initiate growth from later cultivation of rooted plants. The study reported about 90% survival of established seedlings after six months. This percentage refers to emerged seedlings rather than all seeds sown. [Vargas-Luna et al. 2026]
Both propagation methods supply plants for conservation collections but have different requirements. Sowing uses varied seed material and can be carried out without a tissue culture laboratory. Propagation from seedling fragments requires sterile medium, control of shoot growth, separate rooting and acclimatisation. The studies from 2020 and 2026 describe plant production under controlled conditions. Survival after introduction into natural sites requires further field observation. [Vargas-Luna et al. 2026] [García-González et al. 2020]
Synonyms and names in the literature
Echinocactus parryi · Emorycactus parryi [2-WWW]