How do cactus plants look fully grown?

The look of a fully grown cactus depends upon the particular cactus. For example, jumping cactus [Cylindropuntia fulgida] sheds its perilous spines once it's fully grown and heading into old age. In the way of another example, old man cactus [Cephalocereus senilisand Oreocereus spp] becomes enveloped in a downy beard from its fine, long, soft, white outer spines. As yet another example, the giant saguaro cactus [Carnegiea gigantea] finds its towering columnar profile enhanced with branching arms once fully grown.