Watermelon peperomia is the common name used for a popular species from the Peperomia genus named Peperomia argyreia. Watermelons refer to their flowers that mature into bright yellow fruit. The mini watermelon peperomia only grows up to 6 inches and because of their small bushy rosette appearance, they're best suited when grown outdoors as a ground cover or grouped together with other plants indoors. The leaves grow up to 2 inches wide and 1 inch long.