It’s easy to see why the Mexican Fence Post (Pachycereus marginatus) is used as a living fence in Mexico, where it originates. Cuttings are planted where a fence is desired. They soon take root and form an effective and attractive barrier. The Mexican Fence Post will eventually reach 20 feet tall, and will remain as straight as it is in this photo.
I think it’s an exceptionally attractive cactus, and I wish I had acquired a few more. The P. marginatus does not grow arms. It branches from the bottom. I planted this specimen on the east side of my garden, as it prefers partial shade. This cactus does require some protection at temperatures below 25°. I protect the growing tips by placing Styrofoam cups on the tops, as is the practice in this region.