Answer: If you are going to use the plums for canning or jelly, you can pick them when the bloom (whitish waxy coating) first appears and the fruits are still a bit tart. When fully ripe, the plums will fall from the tree. Plums taste best when allowed to ripen on the tree, but as you have seen, that can be problematic. Some gardeners cover their trees with netting to protect the fruit but that isn't easy on a big tree. If you pick them a bit early, you can bring them indoors to ripen at room temperature, out of direct sun.
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