Melocactus Azureus Description: Melocactus azureus is one of most desirable of the Brazilian melocacti because of its striking frosty blue epidermis, this plant has a reputation for being more difficult to cultivate than most.
Stem: Globose, to cylindrical (9-)14-30(-45 cm) tall and 14-20 cm in diameter, green, grey-green, never glaucous (subsp. ferreophilus) or intensely glaucous, especially when young (subsp. azureus), with mucilage present in the chlorophyllous cortical tissues
Ribs: 9-10(-12, acute, triangular in cross section.
Areoles: 1,5-2 cm apart.
Spines: Spines black to reddish, overlaid with grey, some hooked in seedlings.
Central spines: 1-3(-4) slightly curved to straight 2-4,6 cm long.
Radial spines: 7-11 very stout, lowermost longest up to 5 cm long.
Cephalium: 3,5-12 tall, 7-10 cm wide, with white wool (subsp. ferreophilus) or brown wool (subsp. azureus) and conspicuous reddish bristles that protrude noticeably from the cephalia in subsp. ferreophilus (but never exerted in subsp. azureus).
Flowers: Small 15-23 mm long 4-11 mm in diameter pink to magenta, with approx. 25 perianth-segments visible from above.
Flowering Time: Spring to late autumn (fall).
Fruits: Small, white to pale pink above 15-29 mm long, 3-10 mm across. Not produced on isolated plants (self-sterile).
Seeds: Smooth 1-1,7 x 0,9-1,5 mm wide.
Chromosome number: 2n = 44.
Cultivation and Propagation: These tropical cacti are not the easiest things to grow and aren’t plants for beginners.
Growth rate: It is a relatively rapidly growing given the best conditions.
Soils: It likes very porous standard cactus mix soil.
Repotting: The root system is weak and generally resents being repotted and can take a long time to re-establish. Use pot with good drainage.
Light: They preferes very bright light, not as much as the most arid growing cacti, but plenty nonetheless. Tends to bronze in strong light, which encourages flowering and heavy spine production.