A new and distinct plum tree variety, Prunus salicina, cv. `Suplumthirtyseven` characterized by heavy and consistent production of early-season yellow-fleshed purple-black plums that have aromatic sweet flavor, excellent juiciness, and high sugar content (17 degrees brix). The combined traits of the new variety constitute superior quality relative to other commercial plum varieties ripening in `Black Beaut` (unpatented) ripening season in the San Joaquin Valley, Calif.