What adaptations has a cactus made to survive within its environment?

The old man cactus [Cephalocereus senilis] is found in subtropical and tropical Mexico. It adds blue green color to Mexican seashores and mountains. It's a steady growing cactus that slowly reaches an adult height of 50 feet/15 meters within its 200+ year life span. That's in the wild. But in cultivation, they rarely get any taller than 3 feet/90 centimeters.

The old man cactus is known for its long, silky spines that may provide a beard like cover to the upper stem. It also is known for its beautiful, yellow, white or pink blossoms that flower briefly at night. But an audience has to wait until the cactus is at least 20 years old before seeing such a spectacular night show of color and smell.