Kadenicarpus horripilus (Lem.) Vázquez-Sánchez 

🌱 Morphology
  A small cactus with a globose to globose-ovoid body, which can grow solitarily or form clumps with age. The epidermis is olive-green and the stems reach approximately 7–18 cm in height and 4–6.5 cm in diameter. The apex appears depressed and is usually covered by abundant white wool. It features conical, laterally compressed tubercles with a rhomboidal base, about 5–7 mm high. Young areoles are covered with white wool that decreases with age. The spination is characteristic: it generally develops one white central spine, straight and extended, with a dark apex, approximately 1.2–1.8 cm long, accompanied by 12–14 radial spines, also white with dark tips, about 9–11 mm long. The combination of prominent tubercles and white spines with dark tips gives the plant a particularly bristly appearance.

🌍 Distribution, habitat and family
It is endemic to Mexico, mainly in the state of Hidalgo, where it appears in the Metztitlán Valley and surrounding areas. It grows at an altitude of approximately 1200 to 1500 m, in very dry semi-desert scrub, occupying crevices and small rock ledges, especially on calcareous substrates and steep slopes. It shares its habitat with numerous cacti native to the Metztitlán Valley. It belongs to the family Cactaceae, subfamily Cactoideae.

The name horripilus comes from the Latin horrere, "to bristle," and pilus, "hair," alluding to the bristly appearance of its spines. The taxon was originally described as Mammillaria horripila by Charles Lemaire in 1838 and subsequently passed through various genera. Kadenicarpus is currently the correct name for this species.

❄️ Temperature · USDA Zone 9b
It tolerates minimum temperatures of down to −4 ºC when dry and with well-acclimated specimens. During cold spells, it should be kept completely dry, especially due to the compact nature of its root system.

☀️ Lighting
It needs plenty of light and several hours of direct sun to keep the body compact and develop dense, well-defined spination. In cultivation protected from intense summer sun, it can tolerate light shade during the central hours, but insufficient lighting causes elongated growth. As a guide for active growth, a DLI PAR of 20–30 mol·m⁻²·day⁻¹ is recommended.

💧 Growth cycle and watering
Winter rest. During the cold period, it must be kept completely dry. In spring and summer, growth resumes and it can be watered abundantly but infrequently, allowing the substrate to dry out completely before the next watering. Due to its origin on calcareous rocky slopes and its root system adapted to well-draining terrain, it does not tolerate persistent moisture well.

🌸 Flowering
The flowers appear in the apical area during spring and summer. They are relatively large compared to the size of the cactus, approximately 2.2–3.1 cm long and 2.5–3.5 cm in diameter, and have an intense magenta color, with a lighter or whitish throat. The intensity of the magenta contrasts especially with the olive-green body and the white spination. The fruits are elongated, initially green with reddish tones and later brownish-yellow upon ripening, about 4–6 mm long.

🌿 Nutrition
During the active growth period, a fertilizer with high levels of assimilable calcium and low nitrogen levels, such as Desert CHOICE® Cactaceae, is recommended, applied once a month when watering. Before flowering, it can be supplemented with Desert CHOICE® Flowering.

This is an inimitable xerophyte grown in Madrid in a high-tech square pot, with the substrate activated with mycorrhizal fungi and biofungicides.

10x10 cm pot