Astrophytum MYRIOSTIGMA 'MULTICOSTATUM' Nuda, Japan

Astrophytum is a genus of succulent plants in the cactus family (Cactaceae), comprising 6 species and numerous cultivars and forms growing on rocky and calcareous soils in the foothills and mountains of northeastern Mexico and Texas.

Members of the genus are known for solitary, globular or cylindrical, ribbed stems and a near-total absence of spines, although some species do possess a few curved needles. The surface can be smooth or covered with white scales that form unusual, light-colored, felted, marbled patterns on the stem surface capable of absorbing moisture. Leaves are absent; the plant body is green, often with a glaucous bloom, decorated with spine-bearing areoles.

The cacti grow very slowly, but bloom early with large, funnel-shaped, yellow flowers, sometimes with a red center, located at the stem apex. The flowers usually wither after two to three days. With proper care, flowering lasts for an extended period from spring to late autumn. Fleshy, pubescent fruits with thin skin contain black or brown seeds.

Astrophytum myriostigma multicostatum nuda has a globular or, less frequently, cylindrical shape. The number of ribs ranges between 9 and 13.

Before sowing, seeds are soaked for 3–6 hours in warm water with added growth stimulants (SUPERthrive, HB-101, Aminosol, Epin, or Zircon), then disinfected for 10 minutes in a weak potassium permanganate solution, air-dried, and sown on the surface of a moist substrate consisting of leaf mold, river sand, and finely crushed charcoal in a 1:1:1 ratio. They are moistened with a spray bottle, covered with film or placed in a greenhouse, and germinated in light, but not direct sun, at a temperature of 20–25 °C (68–77 °F), preferably with a drop in nighttime temperature to 15–18 °C (59–64 °F). Regular ventilation is carried out and uniform humidity is maintained.

Seedlings emerge within 10–30 days, depending on temperature and humidity. The maximum germination period can exceed 45 days. Care must be taken with watering to avoid damaging the seedlings. Prick-potting is carried out upon the emergence of 2–3 true tubercles, after which the plants are transplanted into individual containers. The seedlings, somewhat larger than those of other globular cacti at this stage, develop slowly but steadily. Flowering occurs at 4–6 years of age provided the dormancy regime and good lighting are observed.

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The plant is placed in a sunny location, preferably on a south or southwest window. Access to fresh air and the absence of stagnant moisture are ensured. In summer, the temperature is maintained at 22–30 °C (72–86 °F). In autumn, the plant is prepared for its dormancy period, and toward winter the temperature is gradually reduced to 10–12 °C (50–54 °F) under complete rest.

Watering is performed moderately after the substrate dries out, thoroughly soaking the root ball with water. In the winter period, watering is excluded. With the onset of the growing season, the holding temperature is gradually raised above 12 °C (54 °F); at lower temperatures, the plant cannot absorb water. The first watering is carried out carefully and with a small amount of water.

A stable, shallow pot with a mandatory drainage layer is selected for cultivation. A mineral substrate with the addition of sand, gravel, and crushed brick is used. Repotting is carried out in spring, carefully, trying not to damage the root system, as new roots regrow with difficulty. The Astrophytum is potted into a container not much larger, just enough to accommodate it. Repotting is done from dry soil into dry soil; watering is resumed after 5–7 days so that injured roots can dry. Mature plants, starting from 10 years of age, are repotted rarely, at intervals of 5–6 years and only if roots entangle the entire soil ball.

During the growing season, once every 4 weeks, plants are fed with specialized cactus fertilizers with a reduced nitrogen content at a diluted concentration. Fertilizer is not applied during the dormancy period. The plants poorly tolerate elevated calcium levels in the soil. Shaping is not required. Propagation is carried out by seeds. Offsets are not produced.