In Season: Domestic plums are crimson to black-red with a yellow or reddish flesh; they are in season May through October. European varieties, which peak during the fall months, range from green to blue to purple and have a golden yellow flesh.
What to Look For: Look for plums that are even in color and plump, yielding gently to pressure. Stay away from fruit with wrinkled or broken skin or extremely soft spots. If too firm to use, place in a closed paper bag at room temperature for one to two days.
How to Store: Once ripe, plums can be kept in a plastic bag in the refrigerator up to three days.