ruthbancroftgarden:

Trichocereus santaensis

This tall columnar cactus is from Peru, and it is very similar to the well-known San Pedro Cactus (Trichocereus pachanoi). Some botanists consider it to be just a form of that species with longer spines. In any case, both plants have large white flowers with hairy bases. The hair is still visible on the fruit after the flower has gone by. For a while, Trichocereus was merged into Echinopsis, but now it is once again accepted as a separate genus.

-Brian