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Native to Central Mexico

Description: The thimble cactus, Mammillaria vetula subsp. gracilis (Mammillaria gracilis), is a small cactus with somewhat slender, cylindrical, bright green body clustering and branching freely, but the offsets easily detached. The offsets are easily knocked off so the plant must be handled with care; however, these offsets quickly root if placed on the ground. The tubercles are roundish, each being tipped by stiff white spines, radiating like a star, making the plant look lace-covered. There are one or more longer dark-brown central spines. Creamy white, bell-shaped flowers appear in spring or in late summer-autumn. Eventually, this cactus forms a large, rounded clumps. Typically subsp. gracilis has only 11-16 radials, often lacks central spines, and flowers are less than 12 mm long.

Source: The Encyclopedia of Cacti

Creamy yellow flowers appear in spring or late summer. At maturity, the plant forms an attractive, rounded clump.

Source: Gardening Know How

Scientific classification

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Core eudicots
Order: Caryophyllales
Family: Cactaceae
Subfamily: Cactoideae
Tribe: Cacteae
Subtribe: Cactinae
Genus: Mammillaria
Species: Mammillaria gracilis fragilis

                         – Wikipedia.