Freezing fresh peaches and plums allows you to have fresh, juicy fruits available during any season for use in pies, cobblers or simply for a healthy snack. Most fruits, including plums and peaches, will maintain their quality and freshness for eight to 12 months when stored properly in a freezer at zero degrees Fahrenheit or below, according to the Colorado State University Extension. Choose peaches and plums that are fully ripe before preparing them for freezing.
Wash fresh, ripe peaches in cool water, gently rubbing the skins to help remove bacteria from the skin.
Pack the whole peaches into plastic containers large enough to allow 1/2 inch to 1 inch of space between the fruit and the lid.
Cover peaches with an ascorbic acid mixture containing 1 teaspoon of ascorbic acid for every quart of water. For a syrup pack, prepare a mixture of 4 cups of water, 3 cups of sugar and 1/2 teaspoon of ascorbic acid, and cover the peaches with the syrup. Ascorbic acid, or vitamin C, helps preserve the fruit's color and flavor.
Seal the plastic containers and place in the freezer immediately after packing.
Wash the plums by rubbing the skins gently under cool running water.
Pack whole plums in plastic containers, leaving 1/2 inch to 1 inch of space between the fruit and the top of the container.
Add a syrup mixture of 3 cups of sugar to 4 cups of water to cover the plums if you desire. Adding ascorbic acid (about 1/2 teaspoon) to the syrup mixture will improve the quality of the fruit. Packing plums in syrup isn't necessary; they'll freeze fine simply by freezing the whole fruit.
Place lids on plastic containers and freeze immediately at zero degrees Fahrenheit or below.