Echinocactus polycephalus is a cactus

Cactus

A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

 that occurs in the Mojave Desert

Mojave Desert

The Mojave Desert occupies a significant portion of southeastern California and smaller parts of central California, southern Nevada, southwestern Utah and northwestern Arizona, in the United States...

 region of Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

, California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, and Nevada

Nevada

Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

. It also occurs in the Sonoran Desert

Sonoran Desert

The Sonoran Desert is a North American desert which straddles part of the United States-Mexico border and covers large parts of the U.S. states of Arizona and California and the northwest Mexican states of Sonora, Baja California, and Baja California Sur. It is one of the largest and hottest...

 region of southern California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and northern Sonora

Sonora

Sonora officially Estado Libre y Soberano de Sonora is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided into 72 municipalities; the capital city is Hermosillo....

, Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

.

The stems are sometimes solitary, but more often in clusters of as many as 30, each up to 0.6 m tall. The spines are yellow to red. The fruits are densely woolly, giving the common name "Cotton top cactus". In the past, it was also called "niggerhead

Niggerhead

In several English-speaking countries, Niggerhead or nigger head is a former name for several things thought to resemble a black person's head....

 cactus." The plants grow in some of the most extreme arid environments in the American Southwest, such as Death Valley National Park

Death Valley National Park

Death Valley National Park is a national park in the U.S. states of California and Nevada located east of the Sierra Nevada in the arid Great Basin of the United States. The park protects the northwest corner of the Mojave Desert and contains a diverse desert environment of salt-flats, sand dunes,...

, and the Mojave National Preserve

Mojave National Preserve

Mojave National Preserve is located in the Mojave Desert of San Bernardino County, California, USA, between Interstate 15 and Interstate 40. The preserve was established October 31, 1994 with the passage of the California Desert Protection Act by the US Congress...

. They have a reputation for being difficult in cultivation, and are rarely seen in cactus collections.