Opening/ Closure Status

All outdoor gardens are currently open. The Conservatory and public restrooms remain closed, due to the closure of the U.S. Capitol campus buildings. Please monitor for updates on operating status. USBG resources can be accessed online, including educational materials, virtual tours, and online programs by visiting

Old woman cactus

Mammillaria hahniana (Old woman cactus)
Plant Botanical Name: 
Mammillaria hahniana
USBG Plant Location: 
Conservatory Room Location: 
World Deserts
Plant Threat Level: 

Mammillaria hahniana is commonly known as the old woman cactus because of the grayish hairs that protect it from the harsh sun common to its native habitat in the Mexican state of Guanajuato. Mexico is an important center of diversity for the Cactus family, containing more than 500 species and possessing the highest number of endemic and endangered cacti of any country in the world. Though wild populations of Mammillaria hahniana are still considered vulnerable, widespread propagation of this species by commercial nurseries catering to cactus hobbyists has greatly reduced the demand for plants illegally collected from naturally occurring populations.