Plums are a rewarding fruit to harvest, but timing the pick is everything for maximizing their flavor. Unlike many fruits, plums largely stop increasing their sugar content once harvested. The key to a delicious plum is catching the fruit at the peak moment when the starches have fully converted to sugars on the tree. This guide helps identify that perfect moment for harvest, ensuring you pick a fruit bursting with natural sweetness.
General Timing and Seasonal Factors
The annual harvest window for plums varies significantly based on the specific type of plum being grown. Plums are broadly classified into two main groups. Japanese plums, typically large and juicy, are the first to mature, with their season generally running from mid-summer (July through August). European plums, often used for prunes or preserves, tend to have a later harvest period, ripening from late summer through early fall, peaking between August and September. Local climate conditions also heavily influence the exact timing; a cool spring or excessive heat can shift expected dates by several weeks. Therefore, while the cultivar provides a broad framework, the true readiness of the fruit must be determined by direct observation on the tree, not simply by the calendar.
Specific Physical Indicators of Ripeness
Determining plum ripeness requires a combination of sensory checks, as no single indicator is entirely reliable. The first visible sign is the color change, which must achieve the deep, uniform hue specific to the variety (e.g., rich purple, deep red, or golden yellow). However, color change is a necessary but not sufficient condition, as plums often develop full color before sugars have fully developed.
A more reliable test involves gently feeling the fruit for firmness. A plum ready for harvest should yield slightly to gentle pressure, indicating the flesh has softened. It should not be rock-hard (immature) nor mushy or overly soft (past its prime).
The best indicator of on-the-tree ripeness is the ease of separation from the spur. A truly ripe plum will detach easily from the branch with a slight upward lift and gentle twist. If the plum strongly resists or requires a hard tug, it should be left to mature further. A taste test provides the final confirmation: a ripe plum will be sweet, juicy, and flavorful, lacking the tartness of an underripe fruit.
Handling Plums After Picking
Ripening Slightly Firm Plums
Plums are climacteric fruit, meaning they continue to soften after harvest, but this process does not significantly increase the sugar content. If a plum is picked slightly firm, it can be ripened indoors at room temperature, out of direct sunlight. Placing the plums in a loosely closed paper bag for a day or two helps concentrate the natural ethylene gas they produce, encouraging softening.
Storage and Handling
Fully ripe plums are delicate and require careful handling to avoid bruising, which can lead to rapid spoilage. During harvest, place them in shallow containers rather than deep baskets to prevent crushing. For storage, ripe plums should be transferred to the refrigerator unwashed, as moisture can accelerate decay. The ideal condition for storing plums is a cool temperature, near 32°F (0°C), and a high relative humidity, such as that achieved in a perforated plastic bag in the crisper drawer. Under these conditions, plums can maintain quality for approximately one to three weeks. When ready to eat, they are best enjoyed after being brought back to room temperature, which helps restore their full aroma and flavor.