Mammillaria melanocentra Poselger
Mammillaria erinacea, Mammillaria melanocentra subsp. melanocentra, Mammillaria runyonii, Neomammillaria runyonii
Mammillaria melanocentra is a small cactus with a flattened globe-shaped stem that grows up to 7 inches (17.5 cm) tall and up to 6 inches (15 cm) in diameter. The stem is green with large, angled tubercles with wooly axils in new growth. Each tubercle is tipped with 7 to 9 needle-like spines that emerge black but age to gray and are tipped black. Flowers are pink, up to 0.8 inches (2 cm) long and about the same in diameter, and usually appear in spring, in a ring on the upper third of the plant body.
How to Grow and Care
To encourage better flowering, allow the plants to enjoy a cooling period in the winter and suspend watering. Unlike many other cacti, which use their ribs as storage devices, the Mammillaria feature raised tubercles, from which spines emerge. When you water, the tubercles will expand to allow for increased water storage. The flowers appear from these tubercles' axils on the previous year's growth, which accounts for their interesting halo effect. The cactus mustn't be exposed to prolonged dampness and sitting water. Never let your cactus sit in a dish of water. Lastly, make sure to fertilizer during the growing season for the best results.
Repot as needed, preferably during the warm season. To repot a cactus, make sure the soil is dry before repotting, then gently remove the pot. Knock away the old soil from the roots, making sure to remove any rotted or dead roots in the process. See more at How to Grow and Care for Mammillaria.
Native to northern Mexico.
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