Strombocactus DISCIFORMIS

Strombocactus DISCIFORMIS - Disc-shaped strombocactus, Strombocactus disciformis.

Strombocactus is a genus in the cactus family (Cactaceae), until recently considered monotypic, but expanded by several species in the last couple of years. Representatives grow in arid locations, on steep precipitous cliffs along the banks of dried-up rivers and canyons. In nature, the plant occurs in the Mexican states of Queretaro, Hidalgo, and Guanajuato.

The plants are small, solitary, with a turnip-like taproot. They have a flattened form. The plants reach a diameter of 8-15 cm (3.1-6 in), a height of up to 20 cm (8 in) in the wild and up to 8 cm (3.1 in) in indoor cultivation. Dentiform tubercles are arranged in spiral rows on the surface. At their apex are small white areoles with slender spines, up to 4 in number. Certain specimens sometimes lack them entirely.

Buds are covered with scales of a reddish-gray shade. Flowers are large, reaching a diameter of 5 cm (2 in), opening during the day. Petals are narrow, white and pale yellow in the middle. The fruits are brown, small in size.

Strombocactus disciformis originates from rocky areas of the Mexican state of Hidalgo. The plant sinks into the soil so deeply that only the uppermost part is visible above its surface. The cactus is usually gray in color. It is difficult to spot before flowering begins. The stem is bluish or gray-blue, up to 8 cm (3.1 in) in diameter and 15 cm (6 in) in height. It consists of low 4-angled tubercles that are strongly blunt toward the top.

Seeds are pre-soaked in a growth stimulant or a weak solution of potassium permanganate, then sown into a substrate of 4 parts fine sand, 1 part sifted slightly acidic peat, and 4 parts crushed brick. The sowing is moistened with a spray bottle, covered with film, and germinated in light, but not in direct sun, at a temperature of 21-26 °C (70-79 °F). Seedlings require ventilation. Waterlogging and drying out of the sowings must be avoided.

Seeds germinate easily; difficulties begin after they sprout. The seedlings must be kept sealed for half a year. Afterward, the sowings begin to be ventilated, gradually acclimating them to dry oxygen. Seedlings are pricked out at the age of 3 months into small pots, with expanded clay and a layer of the same soil previously used placed at the bottom. Maintenance in a warm, shaded location is preferred.

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Strombocactus is one of the most undemanding plants in care. It is best placed in bright locations with light shading on hot days. In autumn and winter, the plant requires maximum illumination. The optimal maintenance temperature is 18-25 °C (64-77 °F), and during the dormancy period 10-15 °C (50-59 °F).

In winter, the plant should be watered once a month. In late March or early April, moisture should be applied so that the soil dries out to 1/3 of its depth between waterings. Water must not stagnate in the tray.

Strombocactus is best grown in soil with a small amount of organic matter and a high content of coarse sand and pebbles. Repotting is carried out in spring, choosing a deep pot with numerous drainage holes. After planting, the root neck can be mulched with a layer of coarse sand or fine gravel to improve moisture drainage. In spring and summer, fertilizers for succulents are applied once a month. In autumn, Strombocactus is transitioned to dormant mode, and fertilization is stopped.