Discocactus is a genus of cacti, highly prized by collectors around the globe. Exactly what it is that makes them so attractive is uncertain. Some of the factors are likely their relatively compact size, unique and showy white flowers, and their slow growth.
The species within this genus are flattened to globose in shape with stems that hardly exceed 3 inches (7.5 cm) in height and are less than 10 inches (25 cm) in diameter. Stems are ribbed and sometimes tuberculate with fuzzy areoles or dense spines. Most plants remain single, but may form clumps. Flowering plants form a wooly terminal cephalium out of which rise the flowers on the end of a long, thin floral tube. The nocturnal flowers are highly fragrant and touted by many growers as the best smelling of all cactus flowers. Discocactus blooms in summer, on and off. The flowers are generally white and open in late afternoon until the following morning.
Light: Discocactus will take full sun, but prefers a little shade in the afternoon.
Water: Water with extreme care after the compost has dried out.
Temperature: During the rest period should be kept at above 59°F (15°C) if grown on its own roots (46°F/8°C if grafted).
Soil: The balance of the potting medium should be sufficient to allow good drainage, 50% compost to 50% gravel, perlite or pumice.
This is probably one of the most difficult cacti to keep growing on its own roots and is almost always seen as a grafted plant. If growing on its own roots is attempted the soil must be extremely free draining, and watering should only take place after the compost has dried out and then only on sunny and warm days.
Discocactus are tropical species, and should be kept warm in winter. The grafted plants are less cold sensitive, but none has any frost tolerance. Mature Discocactus stop growing, and instead divert their energy into growing a cephalium. The cephalium is a specialized flowering head, generally covered with fibers.
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