How to prune old man cactus

Spring, only if rot or dead tissue is present. Cut away rotted or dead tissue with a sterile sharp knife, cutting back to clean, healthy green flesh. Allow the wound to callous in a warm, dry location for several days. Do not trim the white hair-like spines — they protect the plant from sun.

Rarely — only as needed. Old Man Cactus (Cephalocereus senilis) requires no routine pruning. Its columnar form is fixed and should not be shaped or shortened. The only intervention needed is removing dead, brown, or rotting sections at the base with a sterilized blade, followed by thorough drying before any moisture contact.

Cut away rotted or dead tissue with a sterile sharp knife, cutting back to clean, healthy green flesh. Allow the wound to callous in a warm, dry location for several days. Do not trim the white hair-like spines — they protect the plant from sun.