Mammillaria vetula, the thimble cactus, is a species of nipple cactus in the subfamily Cactoideae. It is native to the Mexican states of Hidalgo, Guanajuato and Querétaro. Two subspecies are recognized M. vetula subsp. vetula and M. vetula subsp. gracilis. While the former is usually considered too plain to be grown as an ornamental plant, the latter is one of the most widespread mammillarias in cultivation.
Taxonomy
Mammillaria vetula comprises two subspecies, M. vetula subsp. vetula and M. vetula subsp. gracilis, which were originally thought to be distinct species. M. kuentziana and M. magneticola are considered synonyms of M. vetula subsp. vetula. The specific epithet vetula means "little old one". The common name "thimble cactus" refers to the resemblance of the stems to little thimbles.
Description
Mammillaria vetula is a succulent subshrub which forms clusters of globose to short-cylindric, bluish-green stems with axils that may be naked or slightly woolly. In M. vetula subsp. vetula, young plants have 25 to 40 radial spines, increasing to 50 as they mature, and they remain white. Central spines number 1 or 2, but up to 5 to 9 have been observed in some specimens in Hidalgo. These spines are reddish-brown and about 10 mm long. The flowers are funnel-shaped, lemon-yellow, approximately 15 mm in length and width, with white (sometimes orange-yellow) stigmas. The fruit is dull pink, and the seeds are black.
Mammillaria vetula subsp. gracilis is prolific, producing offsets that detach easily. Its stems are cylindrical, up to 13 cm long and 1 to 3 cm wide, with naked axils. It has 11 to 16 radial spines, 3 to 8 mm long, bristle-like, and chalky white (sometimes tipped brown in smaller variants). Central spines are absent or number up to 5 in mature plants, measuring 10 to 12 mm long and stronger than radials, either white or dark brown. The flowers are 12 mm long and wide, pale yellow with a pinkish or brownish midstripe. The fruit...
