An emerald grape was a type of grape used to make emerald wine.
During the Age of the Empire, Captain Hiram Zataire served ISB Agent Kallus emerald wine aboard the Lawbringer, commenting that despite Lothal's greenness, its grapes "were as sour as Hutt punch." Kallus listened with feigned interest, desiring only to engage in small talk in order to keep the measure of the captain.
Emerald wine appeared in titles such as The Courtship of Princess Leia and Scourge, which are considered part of the Star Wars Legends continuity and not canon, but the grapes used in making it were only mentioned in the canon novel The Rebellion Begins, a novelization of Star Wars Rebels: Spark of Rebellion.