A small one in my collection
From southern Mexico, Isolatocereus dumortieri is a basally branching tree like cactus to 50 feet tall. It can eventually form a trunk a foot thick. The areoles on older plants can be very close together, nearly forming a solid line similar to Pachycereus marginatus. Two inch white nocturnal flowers are produced near the stem tips followed by an oval red fruit.
Another Home Depot find. This one is about 4 inches thick and 6 inches high. Since it gets so huge I'll have to pick a place for it carefully in the yard.