Gymnocalycium HORSTII x TILLIANUM

Gymnocalycium HORSTII x TILLIANUM - Horst's chin cactus x Till's chin cactus, Gymnocalycium horstii x tillianum, Horstillianum.

Gymnocalycium is a genus of plants in the family Cactaceae, comprising about 70 species widely distributed in South America, especially in Argentina, Brazil, Paraguay, Uruguay, and Bolivia at altitudes of 800-3000 m (2,600-9,800 ft) above sea level, on granitic and clayey soils.

Gymnocalyciums are valued for the graceful contours of their stems, which are usually globose and flattened, with a diameter of 4 to 15 cm (1.6 to 5.9 in), while their height is approximately half of the diameter. The primary stem coloration varies from grayish-green to brownish-green, sometimes with an almost gray or almost brown tint. Some cultivars feature unusual red or yellow stems devoid of chlorophyll; such plants are capable of developing only when grafted. 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. The flowers are funnel-shaped with a short tube, form from areoles at the apex of the stem, and open during the day. The flower tubes in representatives of this genus, unlike most other cacti, are devoid of bristles and hairs and are covered with smooth scales. Coloration varies from white and pink to red, yellow, greenish, or brownish-yellow. The fruits are oblong, juicy or dry, containing large black seeds with a texture characteristic of the genus.

Gymnocalycium horstii x tillianum is a hybrid with a flattened-globose body, up to 8-10 cm (3.1-3.9 in) in diameter. The stem is light green or gray-green with a glossy surface. The ribs are broad and rounded, with large areoles. The spines are white, thin, bent away from the body, and can be hooked or straight.

It blooms in summer. The flowers are large, funnel-shaped, white or with a slight pinkish tint, up to 6 cm (2.4 in) in diameter. They are positioned at the crown. The fruits are oval, green or purple, fleshy. The seeds are large, black, with grooves.

The 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. The germination temperature is 22-26 °C (72-79 °F).

Seedlings appear in 7-15 days. The maximum germination period is up to 25 days. Pricking out is carried out when the first spines appear. Young seedlings develop rapidly and tolerate transplanting well.

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It is placed on south- or east-facing windows with access to bright diffused light. In spring and summer, a certain amount of direct sun is tolerated. Regular ventilation is desirable, especially in hot weather.

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

A loose mineral substrate with the addition of leaf mold, sand, and brick grit is used. Repotting is carried out in spring when necessary. Good drainage is mandatory.

During the growth period, mineral fertilizing is applied once every 3-4 weeks. Low-nitrogen cactus fertilizers are used. In autumn and winter, feedings are not applied.

Formative pruning is not required. Propagation is carried out by seeds. The formation of offsets is occasionally possible on older plants. Flowering begins in the 3rd to 4th year when dormancy conditions are observed.