Plum trees begin bearing fruit about 4 years after planting, producing yields of three or more bushels each year. The trees can reach 20 feet in height, with mature trees ready for harvest between late spring and late summer. The fruit is nutritious and tasty, and it is ideal for eating fresh or for canning or preserving into jellies and jams.
Determine whether you have a Japanese, American or European plum tree. Japanese plums are ready for harvesting approximately 2 months after the last winter frost. American plums are generally ready in midsummer, with European varieties following a couple of months later.
Watch for color changes in your plums. A change in color indicates ripening. However, Ohio State University warns that it is difficult to detect ripening solely based on color unless you know the specific cultivar of your plum tree.
Feel the fruit to determine its stage of ripeness. Fully ripe plums will feel slightly soft and yield to slight finger pressure. Gently apply pressure to the fruit with your thumb to check for softness. The skin will feel powdery, and the fruit will give off a pleasant aroma. Less ripe fruit will feel firm and smooth.
Avoid harvesting plums that are hard, bruised, discolored, cracked, broken or shriveled. This may indicate disease or rotting.
Remove any diseased or damaged fruit immediately to prevent contaminating nearby fruit. Rotting fruit left on your tree will attract wasps and other pests. Do not allow dropped fruit to rot on the ground below your tree.
Pick ripe plums by the stalk to prevent bruising. The stalk should snap easily. Be careful not to break delicate branches, as this increases the risk of rot and disease in your tree.
Leave plums that you intend to eat immediately after harvesting on your tree as long as possible. If you intend to use the fruit for canning or cooking, harvest just before the fruit is fully ripe. Fully ripened plums do not last long off the tree.
Store ripe plums in the refrigerator to prevent rotting. You can store under-ripe plums in a paper-lined container in a dark area at room temperature. The fruit will continue to ripen over the several days.