Gymnocalycium BAYRIANUM

Gymnocalycium BAYRIANUM - Bayr's gymnocalycium, Gymnocalycium bayrianum.

Gymnocalycium is a genus of cacti in the cactus family (Cactaceae), comprising about 70 species. All of them grow in South America - in Argentina, Brazil, Paraguay, Uruguay, and Bolivia, at elevations from 800 to 3,000 m (2,625 to 9,843 ft) above sea level, on granitic and clay soils.

The stem is usually globose and flattened, from 4 to 15 cm (1.6 to 5.9 in) across, with height roughly half of that. Coloring ranges from greyish-green to brownish-green, sometimes nearly grey or nearly brown. Ribs are distinctly pronounced, bearing tubercles, with spines moderately rigid and often curved back.

Flowers are funnelform, with a short tube, developing from areoles at the apex of the stem and opening during the day. Coloring ranges from white and pink to red, yellow, greenish, and brownish-yellow. Fruits are oblong, succulent or dry, with large black seeds.

Bayr's gymnocalycium is a species from the Argentine provinces of Salta and Tucuman, where it grows at elevations from 1,000 to 1,500 m (3,281 to 4,921 ft) above sea level. The plant is solitary, with a flattened-globose stem 4-5 cm (1.6-2.0 in) high and up to 10 cm (4 in) across.

Stem coloring is bluish-green, often with a reddish hue that intensifies in bright sun. Spines are stout, curved back, and pressed against the stem. Flowers are funnelform, creamy-white, up to 3 cm (1.2 in) long and about 4 cm (1.6 in) across.

Gymnocalycium seeds are large for cacti, black, with the tuberculate surface characteristic of the genus, ripening in oblong fruits. Soaking them is impractical, so the substrate itself is sanitized: before sowing, it is drenched with a weak potassium permanganate solution and dried. Scarification and stratification are not required.

Sowing is carried out across the surface of a moist substrate with acidity around pH 6.5, without burying. Sowing is moistened from a spray bottle with a growth stimulant solution: SUPERthrive, HB-101, Aminozol, Epin, or Zircon, covered with a lid or placed in a greenhouse propagator, and germinated at a temperature of 22-26 °C (72-79 °F) with regular ventilation.

Under favorable conditions, the first sprouts appear in as little as 7 days, main germination is completed within 7-15 days, and individual seeds may delay up to 25 days and longer. Pricking out is carried out upon the appearance of the first spines: seedlings develop quickly and tolerate transplanting well.

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The plant is placed on a south- or east-facing window with bright diffused light. In spring and summer, a certain amount of direct sun is permissible. In hot weather, regular ventilation is desirable.

In summer, the temperature is maintained at 22-28 °C (72-82 °F), and in winter at 8-12 °C (46-54 °F) with complete dormancy. Cool, dry overwintering is mandatory for flowering.

Watering is moderate, only after the substrate has dried out completely. In winter, watering ceases entirely.

A loose mineral substrate is used, with the addition of leaf mold, coarse sand, and crushed brick. Drainage must be placed at the bottom of the pot.

Fertilizer is applied during the growth period once every 3-4 weeks, using a cactus fertilizer low in nitrogen. In autumn and winter, fertilizers are not used.

Repotting is carried out in spring, as needed. Shaping is not required. Old plants sometimes develop offsets, which can also be used for propagation.