Sulcorebutia rauschii f. violacidermis

Geographic & Climate

Geographic Coordinates: Zudañez, Chuquisaca Department, Bolivia (Approx. 19°07'S, 64°42'W).

Climate Classification: Cwb (Subtropical highland climate).

Habitat Characteristics: Native to high-altitude mountainous regions at elevations of 2,700–3,200 meters. It grows in rock crevices, rocky slopes, and gravelly soils where it is exposed to harsh solar radiation and significant diurnal temperature fluctuations (warm days and freezing nights).

Botanical Morphology

Diagnostic Features: A miniature, globose cactus distinguished primarily by its intense violet to deep purple epidermis, which definitively separates this forma from the standard green S. rauschii. The stems are usually slightly flattened at the apex, measuring 2-4 cm in diameter, with tubercles arranged in distinct spiral formations. The areoles are woolly, bearing extremely short, thin, black pectinate spines that lay completely flat against the stem in a distinctive herringbone pattern. Flowers are bright magenta, funnel-shaped, and usually emerge from the basal or lower part of the stem in late spring to early summer.

Growth Habit: A slow-growing, heavily clustering geophyte. Over time, it offsets prolifically from the base to form dense, low-growing cushions or mounds. It is a summer grower requiring a strict, dry winter dormancy period to encourage blooming and maintain its compact structure. Mature single heads rarely exceed 2 inches in height.

History & Etymology

Etymology: Sulcorebutia is derived from the Latin word "sulcus" (meaning furrow or groove) combined with the genus Rebutia. The specific epithet rauschii honors Walter Rausch, the renowned Austrian cactus explorer who discovered the species. The forma epithet violacidermis is a combination of the Latin "violaceus" (violet) and the Greek "derma" (skin), directly referencing its remarkable purple pigmentation.

Historical Context: The parent species was first documented during Walter Rausch's expeditions in Bolivia. The violacidermis form is a nursery-selected mutation bred specifically for its striking, deep purple coloration. It quickly became highly sought-after in the horticultural world due to the stunning visual contrast between its dark violet body, black spines, and vivid magenta blooms, making it a premium collector's specimen.