There are several different types of saguaro mutation that do not lead to the formation of the classic fan-shaped crest on the tip of the plant. The study of these related forms may give important insight into the underlying genetic cause of saguaro cristation. They're also just fun to look at!

I suspect that the same defective gene that causes the formation of fan-shaped crests (in combination with physical damage to the growing tip) also causes irregular patterns in the pleats of some saguaros.

Normally, a saguaro arm joins the main trunk at a ring-shaped joint. Rarely, an arm or trunk will split smoothly without the ring, forming a "Y" shape. I suspect this is also evidence of the defective gene; sometimes a "Y" is also accompanied by irregular pleating.

These are called "watermelon" saguaros because the arms form in clusters of short segments which resemble a pile of melons.

This mutation in the barrel cactus appears similar to the "watermelon" saguaros.

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