Astrophytum ORNATUM 'MIRBELLII'

Astrophytum ORNATUM 'MIRBELLII' - Astrophytum ornatum 'Mirbellii', ornate bishop's cap 'Mirbellii'.

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

Representatives of the genus are known for solitary, spherical or cylindrical, ribbed bodies and virtually no spines, although some species do have a few curved needles. The surface can be smooth or covered with white flecks forming unusual, pale, felted, marble patterns on the stem surface capable of absorbing moisture. There are no leaves; the plant body is green, often with a glaucous bloom, adorned with areoles and spines.

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

Astrophytum ornatum 'Mirbellii' is the most robust form, having a spherical shape at the beginning of growth, then an elongated one, with a stem height of 30-35 cm (12-14 in) and a diameter of 10-20 cm (4-8 in). The stem itself is dark green, divided into 6-8 ribs that are straight or slightly curved. The stem surface is covered with silvery flecks whose clusters create the appearance of bands. Located on the ribs are areoles with white pubescence and 5-10 straight yellow-brown spines of varying lengths (the largest 4 cm (1.6 in)). Pale yellow flowers open during the day, usually in early summer, and reach a length of 7-9 cm (2.8-3.5 in). Oval green fruits contain several black-brown seeds that, upon ripening, split open to form a peculiar star. The cultivar 'Mirbellii' is distinguished by long golden-yellow translucent spines. The flecking is less pronounced than in the typical species.

Before planting, seeds are soaked for 3-6 hours in warm water with the addition of growth stimulants (SUPERthrive, HB-101, Aminosol, Epin, or Zircon), after which they are disinfected for 10 minutes in a weak solution of potassium permanganate, then air-dried and sown superficially 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 in a greenhouse, and germinated in the light, but not in direct sun, at a temperature of 20-25 °C (68-77 °F), with a night temperature drop to 15-18 °C (59-64 °F) desirable. 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 so as not to ruin the seedlings. Pricking out is carried out when 2-3 true tubercles appear, after which the plants are transplanted into individual containers. Seedlings, somewhat larger than those of other spherical cacti at this time, develop slowly but steadily. Flowering occurs in the 4th-6th year subject to a dormant regime and good lighting.

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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 moisture stagnation are provided. Summer temperature is maintained at 22-30 °C (72-86 °F). In autumn, the plant is prepared for a dormant period, and by winter the temperature is gradually lowered to 10-12 °C (50-54 °F) during complete rest.

Watering is carried out moderately after the substrate dries out, thoroughly soaking the root ball with water. In the winter period, watering is eliminated. With the arrival of the growing season, the keeping temperature is gradually raised above 12 °C (54 °F); at temperatures below this, the plant is incapable of absorbing water. The first watering is done carefully and with a small amount of water.

A stable and shallow pot with a mandatory drainage layer is selected for cultivation. A mineral substrate with the addition of sand, gravel, and brick chips is used. Repotting is carried out in spring, carefully, trying not to damage the root system, since new roots grow back with difficulty. The astrophytum is transferred into a pot not much larger, just so it fits in it. Repotting is carried out from dry soil to dry soil; watering is done after 5-7 days so that damaged roots 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 soil ball.

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