The best way to tell if plums are ready to harvest is by the fruit's firmness and taste. Plums should be just beginning to become soft and should taste sweet and juicy.
Japanese plums are harvested firm ripe. The early maturing varieties will need to be harvested several times over a period of weeks, because not all the fruit will be ready at the same time. The later varieties usually can be harvested at one time. To get the fruit to ripen indoors, keep them between 60° and 80° F. Higher or lower temperatures may cause internal browning, mealiness, or off flavors. For longer term storage, temperatures between 31° to 32° F will provide the optimum storage conditions for about 2 weeks. This narrow temperature range is difficult to maintain accurately in home refrigerators.
European plums are harvested just as they begin to soften and the background color on the skin of the fruit becomes yellow.
Prunes are allowed to ripen fully on the tree. Wait until a few fruits naturally fall, then harvest completely and allow them to dry naturally.
