Mammillaria duwei Rogoz. & P.J.Braun
Mammillaria crinita subsp. duwei, Mammillaria nana subsp. duwei, Mammillaria trichacantha subsp. duwei
Mammillaria duwei is a small, slow-growing cactus that grows either solitary or in clumps. The stems are up to 1.6 inches (4 cm) tall and 2.4 inches (6 cm) in diameter. They are dark green, globose to short cylindrical, and have 0 to 2 central spines and 28 to 36 radial spines per areole. The radial spines are thin, white, brownish at base, interlacing, and densely wrapped against the body. The central spines are yellowish and hooked. Flowers are yellowish-cream to light yellow, funnel-shaped, and up 0.8 inches (2 cm) in diameter.
USDA hardiness zones 9b to 11b: from 25 °F (−3.9 °C) to 50 °F (+10 °C).
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, Mammillaria feature raised tubercles, from which spines emerge. When you water, the tubercles will expand to increase water storage. The flowers emerge from the axils of these tubercles 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 fertilize during the growing season for the best results.
Repot as needed, preferably during the warm season. To repot Mammillaria, 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. Treat any cuts with a fungicide. Place the plant in its new pot and backfill with potting soil, spreading the roots out as you repot. Leave the plant dry for a week or so, then begin to water lightly to reduce the risk of root rot.
See more at How to Grow and Care for Mammillaria.
This species is endemic to Mexico, where it occurs only in the state of Guanajuato.
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