When Do Plums Ripen?
Plums come in two main types:
- European (Prunus domestica)
- Japanese (Prunus salicina)
Within these two groups there are dozens of individual varieties, each with its own optimum range of growth, color of fruit, time of flowering, and optimum time of harvest.
Both groups also have varieties with earlier and later bloom times. Local weather conditions also affect bloom time and ripening of fruit. Get to know your tree by watching how things change from day to day and week to week.
What to Look for in a Ripe Plum
Watch for the following changes in fruit color during the summer:
- Color Changes: Plums come in a wide range of colors including red, purple, yellow, and green when ripe. However, whatever color the plum is there is a slight change and deepening of color as the fruit matures.
- Coating on Surface: Most varieties of plum develop a delicate layer of white powder on the surface of the fruit, indicating ripeness.
- Softness: Ripe plums give slightly when squeezed gently, especially at the tip of the fruit.
- Flavor: The ultimate test is the taste test for sweetness and texture.
How to Ripen Plums After Picking
While plums are always best when picked dead-ripe from the tree, they continue ripening after picking, although some varieties ripen better than others.
To ripen plums which are slightly under-ripe when picked, keep them at room temperature. A kitchen counter out of direct sunlight is usually a good location. The optimum temperature range for plums to ripen is between 68º and 77ºF (20º and 25ºC).
Putting the unripe plums in a paper bag traps ethylene gas, which is naturally emitted by ripening fruit. The gas accelerates the ripening process. However, plums will also ripen up on a plate or in a bowl in the open.
If you have a large quantity of unripe plums, you can store them unripe for up to four weeks by keeping them at a temperature between 31º and 32º (-.5º and 0ºC) at high humidity. Take the plums out of refrigeration and let them ripen at room temperature over a period of three to five days.
Storing Ripe Plums After Harvest
Picking plums ripe from the tree gives you the best flavor. Treat ripe plums gently because they bruise easily. Store them in the refrigerator in an open plastic container or bag where they will keep for up to four weeks. Before, eating, let plums warm to room temperature for maximum flavor.
