Peniocereus greggii var. transmontanus
Native to the American southwest and northern Mexico, Peniocereus is a genus of a dozen or so species of vining cactus with large underground tubers. They normally grow under bushes and small trees, twining their stems upward through the foliage for support. All species produce large white nocturnal flowers.
Peniocereus should be grown in a fast draining cactus mix. They need bright shade to part sun and moderate water spring through fall, but should be kept dry through the winter. Plants can be propagated by cuttings and seeds. I have two species of Peniocereus, click below.