Last fall I went to Tuscon Arizona to see Saguaro cacti and took this pictue. Saguaro are an iconic cactus that symbolizes the American Southwest (even though they only grow in a small part of it). These cacti are huge, this one is at least 30 feet tall. They also grow very slowly and live for a long time. Not every cactus will grow a side arm, but ones that do are at least 75 years old. Saguaro don't have any growth rings so you can't tell how old one is, but can live in excess of 150 years.
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From @lorax4096