Scientific Name
Epithelantha micromeris (Engelm.) F.A.C.Weber ex Britton & Rose
Common Names
Button Cactus, Ping-pong Ball Cactus
Synonyms
Mammillaria micromeris, Epithelantha micromeris subsp. micromeris, Epithelantha micromeris var. micromeris, Epithelantha petri
Scientific Classification
Family: Cactaceae
Subfamily: Cactoideae
Tribe: Cacteae
Subtribe: Cactinae
Genus: Epithelantha
Description
Epithelantha micromeris is a small cactus with globular stems covered with pale grey spines. The stems grow up to 2 inches (5 cm) tall and up to 1.6 inches (4 cm) in diameter. The density of its spines gives it the illusion of being completely grey, making it very difficult to see the green color beneath. Flowers are small, pink-white, often considered to be some of the smallest of the cacti. They give way to a bright red, cylindrical fruit that contains several black seeds and also is edible.

Hardiness
USDA hardiness zones 8b to 11b: from 15 °F (−9.4 °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 allow for increased 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.
Learn more at How to Grow and Care for Mammillaria.
Origin
This species occurs in the United States in Arizona, New Mexico, and Texas, and in Mexico in the states of Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, and Zacatecas.
Subspecies and Forms
Links
- Back to genus Epithelantha
- Succulentopedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus