Biggest of all, the Saguaro, Carnegeia gigantea, sometimes reaches 15m (45ft) in height. Older specimens usually have several side branches, sometimes bent into extraordinary curves. Seedlings grow very slowly and large plants only put on about 4 inches a year. The biggest are over 150 years old. This huge structure has, like most , an exterior of vertical ribs which carry the typical rows of spine clusters. These do not, however, deter many creatures from burrowing into the trunks. Chief among these is a species of woodpecker, which hollows a nest cavity from the pulpy . The damaged area soon heals over with a thick, hard layer of scar tissue, so that the woodpecker’s nest is dry and snug.
When the woodpecker leaves the nest hole, it is very often taken over by the little elfin owl: this bird never digs out his own. Other small creatures like rats and mice may make burrows in the cactus stems, while yet others, like snakes, occupy holes made previously.
The large creamy flowers of the saguaro are followed by big pulpy fruits, which the Indians used to gather in great quantities for eating and drying for winter use.