Cylindropuntia echinocarpha flowering near Joshua Tree NP in California. This plants form low bushes with distinct main stem - trunk, each specimen looking like a spiny tree. In the fall the plants will be shivered so no green seen through the spines, and will stand true to their names Silver" and "Gold" cholla - depending on the spine color. Each spine of 'true' Cylindropuntia has a paper-like sheath, and color of spines is actually the color of that sheath.
Flowers are also nice with their shades of green