Perhaps you’ve seen those saguaro cactuses with tops that resemble a series of fists, or maybe broccoli. It’s as if they experienced a growth spurt and hit an invisible ceiling, resulting in a cartoonish splat.

If so, you are among the lucky few who have encountered a rare crested saguaro, a mysterious top-heavy brute that has no scientifically proven explanation, reports The Arizona Republic, which is part of the USA TODAY Network.

First, a little background on the Arizona native, as saguaros grow naturally only in the Sonoran Desert (a fact roundly ignored by filmmakers who feature the saguaro each time they want to suggest remote desert, even in movies that are set in saguaro-less Texas or New Mexico).

How fast do saguaros grow?

Saguaros grow very slowly, all of one inch in height by the time they are 10 years old. But the next 80 years are a veritable growth spurt, when they attain 15-16 feet.

Growth typically is straight up until a transformative stage when, between the ages of 50 and 70, saguaros sprout the iconic arms. Despite what is seen in comics and cartoons, arms don’t usually grow in the symmetrical “hands up” formation, as fun as that looks.

Instead, saguaros typically have several arms twisting this way and that. Such an arrangement lends a unique look to each specimen.

What causes a crested saguaro?

The rarest look of all is that of the crested saguaro.

Tens of thousands of cactuses grow in Saguaro National Park near Tucson, Arizona. Yet according to the park's website, roughly 25 crested saguaros have been found within its boundaries.

Biologists have yet to scientifically prove what causes the prickly fan-shaped growth that gives the saguaros their name. It may be a genetic mutation, or the result of a deep freeze or a lightning strike.

Researchers at Arizona State University even created a garden of crested cactuses, using a genetic mutation to create the fascinating growths.

Rather than try to explain the crested saguaro, simply Instagram it. After all, it seems designed for one thing — to be enjoyed.