Hairy Cactus

"Pilosocereus is a genus of around 50 species of mostly large columnar cacti. The name comes from the Latin for 'hairy Cereus'. Pilosocereus are generally not frost resistant, and should be protected. If one of your specimen is outside and a light frost might occur, the usual way to protect it in Phoenix is to stick a polystyrene cup at the top of each stem."

I have seen the cacti during the winter with coffee cups stuck on the end of each stem but I always thought that the cups were a prank. Who knew? Lol