Mammillaria melanocentra is one cactus that likes plenty of root room, unlike many cacti that prefer to be confined or crowded. It will grow rapidly if regularly repotted to a larger pot to accommodate the roots. If it gets crowded in the pot, its appearance will deteriorate, and become dull.
M. melanocentra has a black central spine that can grow to about two inches long. Notice the nest of black spines in the top center. Melanocentra means exactly that—black center. No mystery associated with this species name!