Julie wonders why this saguaro has three stems (or three trunks, if you prefer). We'd need to do some genetic testing to confirm, but I can think of a few possibilities.
One possibility is that this is actually three plants growing closely together. We'd be able to tell for sure if we compared the DNA from the three stems.
I doubt we'd get permission to do that, however : -)
Looking at the base, it could be that this saguaro was damaged early on in its growth. It's possibly that the growing tip was cut, but that enough of the growing-tip cells remained in three areas and continued to grow. (There are multiple stems on other saguaros damaged by humans in Sabino Canyon.)
The third possibility may have occurred early in this saguaro's life cycle as well. The cells at the tip may have undergone abnormal division, resulting in three separate growing tips.
If you have other hypotheses about this saguaro, please send them my way. Only science can reveal which hypothesis is the correct one. In any case, this is another great saguaro.
Thanks, Julie, for this great question!