PHOTO BY MAX SCHULTE Sydney Luke is suprised by some of the information written on the side of a plant at Stem, a plant shop on Alexander Street that specializes in rare and exotic plants. Imagine a hard-to-find, intensely Instagrammable houseplant, and something like the monstera deliciosa albo variegata, with its iconic broad-split leaves streaked with white, might come to mind. Samantha Mills has one in a gold pot on the counter of her shop. “Her name is Betty,” Mills said, a tribute to The Golden Girls star Betty White. Mills is a co-owner of Stem, a new shop at the corner of Alexander Street and Park Avenue specializing in plants like Betty: hard to find and all the rage.