Ferocactus glaucescens

Ferocactus glaucescens, the glaucous barrel cactus, is a species of flowering plant in the family Cactaceae, native endemic to México.

Description
Ferocactus glaucescens is a solitary or branching cactus with spherical or cylindrical blue-green frosted shoots, growing up to 45 cm in height and 60 cm in diameter. The shoots have slightly depressed apices and 12 to 17 sharp-edged, non-tuberculated ribs with elongated areoles that are often connected. Its yellow spines, which are difficult to distinguish between central and peripheral, can reach up to 3.5 cm in length, with one central spine and 6 to 7 radial spines.

The bell-shaped, yellow flowers of Ferocactus glaucescens are up to 4.5 cm long and 2.5 to 3.5 cm in diameter. Its spherical, whitish or yellowish, red-tinged fruits are fleshy, reaching lengths of up to 2.5 cm and covered in yellowish, ciliated scales.

Distribution
This species is native to the limestone hills and dry forest of Hidalgo, Guanajuato, Querétaro, and San Luis Potosí states of Mexico at elevations of 550 to 2300 meters.

Taxonomy
First described as Echinocactus glaucescens in 1828 by Augustin Pyramus de Candolle, the specific epithet "glaucescens" comes from the Latin words "glaucus" for 'blue-green' and "-escens" for 'becoming', referring to the color of the shoots. In 1922, Nathaniel Lord Britton and Joseph Nelson Rose reclassified it into the genus Ferocactus.

Cultivation
In cultivation in temperate regions it must be grown under glass. It has gained the Royal Horticultural Society's Award of Garden Merit. There is a spineless form, Ferocactus glaucescens forma nuda (inermis).