Astrophytum COAHUILENSE

Astrophytum COAHUILENSE - Coahuila bishop's cap, Astrophytum coahuilense.

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

Representatives of the genus are known for their solitary, globose or cylindrical, ribbed bodies and virtually complete absence of spines, although some species do have a few curved needles. The surface can be smooth or covered with white flecks forming unusual, light-colored, felt-like, marbled patterns on the stem surface that are capable of absorbing moisture. There are no leaves; the plant body is green, often with a glaucous bloom, adorned with areoles bearing spines.

These cacti grow very slowly, but in return bloom early with large, funnel-shaped, yellow flowers, sometimes with a red center, situated at the apex of the stem. The flowers usually fade 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 coahuilense has a gray-green stem, initially globose, columnar with age, without lateral shoots, completely covered with a thick layer of grayish-white floccose flecks. The largest specimens found in the wild at up to 150 years of age reach 50 cm (20 in) in height and over 20 cm (8 in) in diameter. In older plants, deep transverse furrows are often observed in the lower part of the stem.

The ribs (always 5) are initially acute, later rounded with wavy margins. The areoles become prominently noticeable only after flowering. The flowers are yellow with an orange or pinkish center, 5-7 cm (2-2.8 in) in diameter. The fruits are crimson, dehiscing in their lower part, containing a large number of seeds.

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

Sprouts appear within 10-30 days, depending on temperature and humidity. The maximum germination period can exceed 45 days. Caution must be observed with watering to avoid damaging the seedlings. Pricking out is performed when 2-3 true tubercles appear, after which the plants are transplanted into individual containers. The seedlings, somewhat larger than those of other globose cacti at this stage, develop slowly but steadily. Flowering occurs at 4-6 years of age under observance of the dormancy regime and good lighting.

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

Watering is carried out moderately, after the substrate dries out, fully soaking the root ball with water. During the winter period, watering is excluded. With the onset of the growing season, the ambient temperature is gradually raised above 12 °C (54 °F); at lower temperatures, the plant is incapable of absorbing water. The first watering is performed cautiously with a small amount of water.

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

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