Synonyms:

Echinocactus pflanzii

Habitat:

Gymnocalycium pflanzii, a captivating cactus species, can be traced back to a diverse range of habitats in South America. It is found in the southeastern regions of Bolivia, spanning across Cochabamba, Chuquisaca, Potosí, Santa Cruz, and Tarija. Additionally, its natural distribution extends to the northwestern areas of Paraguay, including Alto Paraguay and Boquerón, as well as the northern provinces of Argentina, namely Salta, Jujuy, and Tucumán.
When it comes to its preferred altitude, Gymnocalycium pflanzii demonstrates its adaptability, thriving at elevations ranging from 500 to 2,500 meters above sea level. This impressive range allows the species to inhabit various ecological niches and adapt to different conditions.
The cactus is often found in its natural habitat semi-buried within deep, nutrient-rich sandy soil. It displays a preference for sunny rocky areas, taking root on slopes or finding shelter under spiny shrubs in the sotobosque. The sotobosque refers to the understory vegetation layer in forests. Gymnocalycium pflanzii appears to flourish at the borders and clearings of the dry Chaco forest, showcasing its remarkable ability to occupy diverse environments.
Despite its widespread distribution, Gymnocalycium pflanzii is fortunate to be abundant and faces relatively minor threats within its range. Subsistence farming, agricultural activities, and goat grazing, while present, do not pose significant dangers to the species in most parts of its extensive territory. This resilience, coupled with its ability to adapt and thrive in diverse settings, contributes to the success and survival of Gymnocalycium pflanzii in its natural habitat. As custodians of these delicate ecosystems, it is crucial to recognize and preserve the diverse range of habitats that this magnificent cactus calls home.

Description:

Gymnocalycium pflanzii is a cactus that usually grows alone or in small clusters. One unique feature is its spines, which bend backward in a distinct way. The stem is flattened and round, measuring about 10-15 cm in diameter and 10 cm tall. It appears pale green but can have hints of olive green or orangish-purple when exposed to full sunlight. The surface of the stem has a soft and velvety texture, and the top part is slightly sunken and covered in wool. The cactus has 10 to 12 thick ribs, divided into rounded shapes, with spaces between them. Its roots are fibrous, and the areoles, which are oval and quite large, have cream-yellowish wool initially, but it turns blackish over time. Gymnocalycium pflanzii has strong and very stiff spines that curve backward. These spines start off blackish with a brown base but change to grey-pinkish or whitish brown with a black point. The flowers are infundibuliform (funnel-shaped) and can be found near the top of the cactus. They have a diameter and height of about 45-50 mm. The outer tepals are spatulate (spoon-shaped) and slightly bent outward, white with a brownish green midrib. The inner tepals are narrower, spatulate, and slightly denticulate, with a white color and a carmine/pink purplish throat. The style is carmine colored with 10-12 lobes of the same color, and the pollen is yellow. As the fruits ripen, they become globose (spherical) and reach about 2 cm in diameter, with a red carmine color. The pulp inside is a vivid cherry-red shade. The seeds of Gymnocalycium pflanzii are tiny, with a reddish shining and smooth testa (outer covering). This species is quite variable, and there are several described varieties and subspecies, with only three or four recognized as official. These include subsp. argentinense from Gonzales, Salta, Argentina, subsp. zegarrae from Tarija, Bolivia, and subsp. dorisie, also from Tarija, Bolivia.

Cultivation:

Cultivating and propagating Gymnocalycium pflanzii can be very rewarding due to its ease of care and abundant flowering. To ensure its well-being, provide a well-drained and relatively rich substrate, avoiding limestone if possible. Gymnocalycium pflanzii grows relatively fast and flowers easily.
For potting, use a very porous cactus mix with good drainage and sufficient space for its root system. Repotting should be done every other year or when Gymnocalycium pflanzii outgrows its pot.
During the summer, Gymnocalycium pflanzii needs moderate to copious waterings, but be careful not to overwater, as it is susceptible to rot. In winter, keep it dry and maintain a minimum temperature of 0°C.
Fertilize Gymnocalycium pflanzii with a high-potassium fertilizer during the summer season to support its growth.
When it comes to hardiness, Gymnocalycium pflanzii is reputedly frost-resistant if kept on the dry side before and during cold weather. However, it’s best to avoid freezing temperatures for safe cultivation.
Regarding sunlight exposure, Gymnocalycium pflanzii tolerates very bright conditions but prefers filtered sunlight or afternoon shade. Indoors, it needs bright light with some direct sun. Be cautious, as too much direct sunlight during the hottest part of summer days may lead to sunburn or hinder its growth. Gymnocalycium pflanzii is an excellent choice for container gardening, and it remains small, making it a visually appealing addition to cold greenhouses, frames, or rockeries. While generally pest-free when grown in good conditions with proper ventilation, Gymnocalycium pflanzii may attract some insects. Red spiders can be controlled by watering from above. Mealy bugs might appear in the new growth, especially among the wool, and can also develop on the roots. Scales are rarely problematic. As for diseases, rot is a minor concern, but proper watering and aeration can help prevent it. Gymnocalycium pflanzii is generally easy to care for and has good resistance against cryptogamic diseases. Fungicides may not be effective if watering and airflow are not properly managed.

Propagation:

Propagation of Gymnocalycium pflanzii is typically done using seeds. These seeds germinate within 7-14 days when kept at temperatures between 21-27°C during the spring season. When sowing the seeds, it’s common to cover them with a glass lid, creating a mini-greenhouse effect. However, once the seedlings have taken root (after about 1-2 weeks), it’s essential to gradually remove the glass cover and ensure proper ventilation. During this early stage, young plants should not be exposed to full sun, as they are sensitive and require protection.
Grafting, except for specific chlorophyll-deprived cultivars, is generally not recommended for Gymnocalycium pflanzii as it does not yield significant benefits. Therefore, seed propagation remains the most reliable and successful method for reproducing this cactus species.

Curiosity:

The genus name “Gymnocalycium” is derived from two Greek words: “Gymno” (γυμνό) means “naked” or “bare.” “Kalyx” (κάλυξ), instead, means “calyx” or “cup-shaped structure,” specifically referring to the outer whorl of a flower. The name “Gymnocalycium” was given to this genus of cacti because its flowers lack the typical calyx, or the outer green structure that covers the base of a flower. In Gymnocalycium species, the calyx is reduced or absent, thus giving them the name “naked calyx.”

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