Synonyms:

No officially recognized synonyms.

Habitat:

Sulcorebutia rauschii f. violacidermis is a nursery-selected form, bred for its intense violet-colored epidermis. The parent species, Sulcorebutia rauschii, is native to the mountainous regions of southern Bolivia. In the wild, it grows on rocky slopes and gravelly soils, nestled in rock crevices at elevations between 2,500 and 3,500 meters, in a dry and well-ventilated environment characterized by strong temperature fluctuations.

Description:

The name Sulcorebutia comes from the Latin sulcus (“furrow”) combined with the related genus Rebutia, referring to the deep grooves between the areoles that characterize these plants. The specific epithet rauschii honors the Austrian botanist and collector Walter Rausch, who contributed to the discovery and dissemination of many Bolivian cactus species. The term violacidermis combines the Latin words violaceus (“violet-colored”) and dermis (“skin”), referring to the violet epidermis, a distinctive feature of this form.

Sulcorebutia rauschii f. violacidermis belongs to the genus Sulcorebutia and to the family Cactaceae. It is a small, globose and compact cactus, often slightly flattened at the apex. The stem, violet to deep purple in color, measures 2-4 cm in diameter and is divided into numerous spirally arranged tubercles, each topped with woolly areoles bearing short, thin, black spines arranged in a herringbone pattern. Over time, the plant forms dense and tight clusters, creating highly ornamental cushions. Its thick, matte epidermis helps protect it from the intense solar radiation typical of the high-altitude habitats where the species originates.

From spring to summer, the plant produces flowers that are relatively large compared to the size of the stem, emerging near the base and forming a vivid contrast with the dark epidermis. The petals are bright magenta to fuchsia, and flowering is abundant in mature specimens grown in bright light. After pollination, small spherical fruits, greenish to reddish in color, develop and, when ripe, release tiny dark seeds.

Cultivation:

This species grows slowly, is easy to cultivate, and is suitable even for beginners.

The ideal soil for Sulcorebutia rauschii f. violacidermis must ensure excellent drainage and good root aeration, as the species is particularly prone to rot under stagnant moisture. A mineral, low-organic mix is recommended, composed of pumice, volcanic lapilli and coarse sand, with a small proportion of universal potting soil or humus.

Watering must be handled with great care, as the species is sensitive to excess moisture. During the growing season, roughly from April to September, water only when the substrate is completely dry. In the hottest months, watering every 10-15 days is sufficient, gradually reducing frequency as autumn approaches. In winter, during the plant’s dormant phase, watering should be almost completely suspended.

This cactus requires plenty of light to maintain its violet color. It thrives in full sun during the cooler hours or in bright and filtered light during summer, with light shading at midday to prevent sunburn. In winter, it can be placed in a sunny position, ideally near a south-facing window.

It requires minimal feeding. During the growing season, apply a cactus-specific fertilizer sparingly. In autumn and winter, when the plant enters dormancy, fertilization should be completely suspended.

Repotting is needed only occasionally, as the plant can remain in the same container for several years. It should be done when the roots fill the pot, preferably in early spring. Use a slightly larger container filled with fresh, mineral and well-draining substrate.

This species is non-toxic to humans and pets. However, its rigid spines can cause minor skin irritation or scratches, so it is advisable to handle the plant with gloves or tongs during repotting.

A hardy species that is rarely affected by diseases, it can nevertheless suffer from excess moisture or poor drainage, which may lead to root rot. In enclosed or poorly ventilated environments, it may also be attacked by mealybugs or, less frequently, aphids, which nest between the tubercles and areoles.

Care tip: to encourage flowering, keep the plant in a cool, dry and bright location during winter, with temperatures between 32 and 50°F (0-10°C).

Propagation:

Sulcorebutia rauschii f. violacidermis is propagated mainly by dividing basal offsets, the simplest and fastest method, which helps preserve the characteristic violet epidermis. Offsets are taken during the warm season with a clean cut, left to callus for a few days, and then placed to root in a dry, mineral and well-draining substrate. Watering should begin only after new roots have formed. In collections, grafting is sometimes used to speed up growth and flowering. Seed propagation is also possible but slower and does not ensure the preservation of the violacidermis form, as it is a horticultural selection.

Curiosity:

The color of this plant varies with the amount of light it receives. When grown in full sun, the epidermis tends to develop darker and more vivid tones.