Opuntia echinocarpa — Engelm. & Bigelow
Cylindropuntia echinocarpa is native to the Southwestern United States and Northwestern Mexico, where it can be found the Sonoran Desert, the Mojave Desert, and Colorado Desert in California and other states.
Silver cholla is a large, tree-like cactus which may exceed 2 m (6.6 ft) in height. Its stems and branches are made up of cylindrical green tubercles (segments) up to 1.5 cm wide and just under 1.0 cm tall. The fleshy tubercles each bear up to 20 long, straight, grayish or yellowish spines which may be nearly 4 cm long. The width of the tubercles is less than twice the length, which helps to distinguish it from buckhorn cholla (Cylindropuntia acanthocarpa), which occurs in a similar geographical distribution.
The flowers are usually greenish yellow, sometimes pinkish or brownish in color. The fruit is lumpy, spiny, and tan in color, with white seeds and a foul scent, reminiscent of rancid butter. It measures up to two centimeters long. Very few fruits reach maturity, and many immature fruits can often be seen lying on the ground below. This plant reproduces mainly through seeds, but its tubercles may break off and have a chance of producing new plants through asexual reproduction. 
- USDA: Cylindropuntia echinocarpa . accessed 3.23.2013
- Mojave Desert Wildflowers, Pam MacKay, 2nd ed., p 223, 266
- Ebert, T.A. (2006). "Density dependent responses of Cacti, Cylindropuntia bigelovii and C. echinocarpa (Cactaceae), in the desert of Southern California, USA". Journal of Arid Environments. 66 (4): 609–619. doi:10.1016/j.jaridenv.2005.11.013. ISSN 0140-1963.
- Bobich, E (2001). "Vegetative Reproduction as Related to Biomechanics, Morphology and Anatomy of Four Cholla Cactus Species in the Sonoran Desert". Annals of Botany. 87 (4): 485–493. doi:10.1006/anbo.2000.1360.
|Wikimedia Commons has media related to Cylindropuntia echinocarpa.|
- Cylindropuntia echinocarpa photo gallery at Opuntia Web
- Jepson Manual Treatment — Cylindropuntia echinocarpa
- Flora of North America
- Cylindropuntia echinocarpa Photo gallery
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