Plums develop their best flavor if left to ripen on the tree. If they feel soft when gently squeezed, they are ripe. Trees will generally need picking several times through the ripening season.
When to Harvest
Homegrown plums are best picked when fully ripe, but can be harvested early and ripened on the counter. Ripe plums may be red, blue, green or yellow, depending on the variety, so it's a little difficult to go by color alone to determine ripeness. As plums ripen, they first change color, then soften, and the skin takes on a powdery appearance and they develop their sweet flavor.
Ripe fruit yields to gentle pressure, especially near the tip.
Ripe plums are sweeter, softer and more prone to bruising.
How To Pick Plums off The Tree
You'll want to gently twist or use a pair of sharp hand pruners to cut the fruit off the tree and place it in your harvesting container. To avoid bruising the fruits handle them carefully, like you would eggs.
How To Store Plums
Do not leave the fruit in your harvesting container(s) once you've got them indoors. Instead, you'll want to start sorting them right away into those that are not quite ripe and those that are ripe. A ripe fruit will yield a bit when pressed very gently. An unripe fruit will be harder to the touch.
The fruits that needs some time to ripen can be spread out on a counter, not touching each other and not in the sun. The rate of plum ripening is determined by room temperatures. Plums ripen quickly at temperatures between 68 and 77 degrees Fahrenheit. Higher or lower temperatures slow the rate of ripening. Plums are more likely to develop off flavors and ripen irregularly when temperatures are above 77 F. These should ripen within 2 to 3 days. Check their ripening progress frequently and discard any fruit that has started to spoil. To speed up the ripening process, place plums in a paper bag and store at room temperature, out of direct sunlight. The plum is ripe and ready to eat when the flesh softens enough that gentle pressure from the thumb dents the skin.
If you want to store unripe plums, keep in mind this is best done at temperatures between 31 and 32 F and at 90 to 95 percent humidity. Commercial growers are able to store plums for two to four weeks under these conditions before ripening. Most home refrigerators are set to function at slightly higher temperatures. This causes problems storing unripe plums at home because temperatures between 36 and 46 F cause chill damage. Fruit that has been chill damaged will not ripen properly and often rots. Therefore, for most home growers, it is best to ripen the fruit before storage.
Once plums have ripened, either on the tree or off, they keep well in the crisper section of the refrigerator. Store ripe plums in an open plastic bag for two to four weeks. Bring them back to room temperature just before eating for best fresh flavor.
