Frailea (Frailea castanea syn. Frailea asterioides) are very small cacti that rarely reach 2 inches in diameter.
Frailea castanea is a summer grower species relatively easy to grow. It is sometime seen as a grafted plant but grows very well on its own roots too. Characteristically, during the dry season plants retract completely under the ground both in the wild and in cultivation too. Growth rate: Fraileas are relatively short-lived plants, only lasting few years (rarely more than 10-15 years in cultivation) and, possible annuals in habitat! In fact they reseed readily around the base of the mother plant from self-set seed if kept reasonably moist during warm weather. It is a good idea to keep restarting them from seed; what looks like a healthy big plant may suddenly die of old age without warning. Soil: Use mineral well permeable substratum with little organic matter (peat, humus), plants may become too elongated if compost is too rich. Repotting: Re-pot every 2 years. Use pot with good drainage. Fertilization: It grows much faster with a low nitrogen content fertilizer in spring and summer. Potassium helps maintaining the plants compact and healthy. Watering: Requires careful watering to keep plant compact. Water sparingly from March till October, the thin, fibrous roots suffer if there is humidity, therefore the plant should be watered only when the surrounding terrain is dry. Keep dry as soon as the temperature starts dropping in October and keep it perfectly dry in winter at temperatures from 5 to 15 degrees centigrade. Hardiness: They need a minimum temperature of 5-10° C (but occasionally temperatures of a few degrees below 0° are not dangerous if kept on the dry side prior to, and during, cold weather). It tends to rot in winter during the resting phase, if kept wet. In the rest period no high atmospheric humidity!! Sun Exposure: Light shade to full sun, its colour tends to richer and darker when grown in light shade. In a shaded position the plants grow faster, but are not flat shaped and dark colored.