Gymnocalycium DENUDATUM

Gymnocalycium DENUDATUM - Spider Cactus, Naked Chin Cactus, Gymnocalycium denudatum, Echinocactus.

Gymnocalycium is a genus of plants in the cactus family (Cactaceae), comprising about 70 species widely distributed in South America, particularly in Argentina, Brazil, Paraguay, Uruguay, and Bolivia at altitudes of 800-3000 m (2600-9800 ft) above sea level, on granitic and clay soils.

Gymnocalyciums are valued for their elegant stem contours, typically globose and flattened, with a diameter of 4 to 15 cm (1.6 to 6 in), while height is about half the diameter. The main stem color varies from grayish-green to brownish-green, sometimes with an almost gray or almost brown tint. Some cultivars feature unusual red or yellow stems lacking chlorophyll; such plants can only develop in a grafted state. The stems are generally distinctly ribbed, with tubercles located on the ribs. The spines are moderately stiff, often recurved.

The plants are valued for their showy flowering. Flowers are funnel-shaped, with a short tube, forming from areoles at the stem apex and opening during the day. Flower tubes in members of this genus, unlike most other cacti, lack bristles and hairs and are covered with smooth scales. Coloration varies from white and pink to red, yellow, greenish, or brownish-yellow. Fruits are oblong, fleshy or dry, containing large black seeds with a texture characteristic of the genus.

The spider cactus has a globose stem up to 10 cm (4 in) in diameter, which elongates with age and forms lateral shoots in the lower part. The epidermis is glossy green and shining. It has 5-8 flat ribs interrupted by small transverse furrows, ribs with weakly defined tubercles. Areoles are few, large, covered with short light brown, later gray hairs.

There are no central spines. Radial spines are most often 3-5, in the lower part of the stem up to 8; they are slightly over 1 cm (0.4 in) long, whitish-yellow, undulatingly curved, and pressed flat against the stem surface. Flowers grow near the crown, are white, sometimes with a pinkish tint, up to 5 cm (2 in) long, with a long floral tube and numerous long narrow petals reflexed outwards. The ovary is short, broad, light green, with sparse scales.

Seeds are sown on the surface of a moist substrate with a pH of about 6.5. Sowing containers are covered with a lid and ventilation is provided. Germination temperature is 22-26 °C (72-79 °F).

Seedlings emerge within 7-15 days. The maximum germination period is up to 25 days. Prick-potting is performed when the first spines appear. Young seedlings develop quickly and tolerate transplanting well.

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Place on southern or eastern windows with access to bright diffused light. In spring and summer, a certain amount of direct sun is acceptable. Regular ventilation is desirable, especially in hot weather.

In summer, temperature is maintained at 22-28 °C (72-82 °F). In winter - 8-12 °C (46-54 °F) during complete dormancy. Watering is carried out moderately, after the substrate has completely dried out. In winter, watering is completely stopped.

Use a loose mineral substrate with the addition of leaf mold, sand, and brick chips. Repotting is carried out in spring when necessary. Good drainage is essential.

During the growing season, apply mineral fertilizers once every 3-4 weeks. Use cactus fertilizers with low nitrogen content. In autumn and winter, fertilizers are not applied.

Shaping is not required. Propagation is carried out by seeds. Occasionally, offset formation is possible in older plants. Flowering begins in the 3rd-4th year when dormancy conditions are observed.