The organ pipe is a large cactus found rarely in the United States, although it is common in Mexico. Organ Pipe Cactus National Monument encompasses the bulk of its U.S. population. Due to a high sensitivity to frost, organpipes are most often found on south-facing rocky slopes at less than 3300 feet in elevation. When it blooms in the heat of May, June, and July, the organ pipe waits until the sun goes down to open its tender lavender-white flowers. Nectar-feeding bats, such as the lesser long-nosed bat, are the primary pollinators of organ pipes.