A new and distinct plum tree variety, Prunus salicina, cv. ‘Suplumfiftyone’ is characterized by having large fruit with dark red flesh. The fruit of the new variety ‘Suplumfiftyone’ is also moderately firm, juicy and has a mild sweet flavor. The date of the harvest of the fruit of the new variety is later than for ‘Black Splendor’ (unpatented). The fruit of the new variety ‘Suplumfiftyone’ ripens with nearly same timing as the fruit of ‘Friar’ (unpatented) but has a dark red flesh compared to yellow-colored flesh for the fruit of ‘Friar’.
