Cacti are native to the Americas and first evolved 30 million years ago—which sounds like a long time—but they’re hundreds of millions of years younger than most other types of plants.

They’re specially adapted to dry environments, having transformed their trunks into thick, green, water-storing tissue and their leaves into spines.

Cacti grow from half an inch to more than 60 feet in height and range from Patagonia to Canada.

They draw in CO2 at night to fuel photosynthesis during the day, then close their pores as temperatures rise to avoid evaporation.

Perhaps the most iconic cactus is the giant saguaro. It’s become a symbol of the American West but grows mainly in Arizona. And very slowly.

It takes 10 years to reach an inch tall. Seventy to reach six feet. By the time it’s 200, it has reached its full height of 40 plus feet.

Along with a tap root to hold it up, saguaros, like most cacti, have a broad shallow root system, just a few inches below the surface. An adult saguaro can use this to suck up 200 gallons of water during a single desert rain storm.

That might make them sound like a good water source, but cacti produce acids and alkaloids to protect themselves; drinking their stored water can make you sick.

The fruits of all cacti, however, are edible. But most are prickly, and many taste bad. The cactus has evolved to be as tough as its environment.