Answer: Grape tree (Coccoloba uvifera) produces edible fruit in early summer. If the fruit on your tree is rotting, you may not be harvesting at the right time. The fruit itself is grape like although a bit tougher than the ordinary grape and it has one large seed as opposed to several small ones. They remain green and hard for a long time but eventually one by one they change to their mature deep purple color. They hang in bunches, each one with a single seed, and are about the size of regular grapes. When fully mature, they become soft and have a sweet-sour taste making them great for use in jams and jellies. Try testing them for ripeness when they just begin to turn deep purple.
Best wishes with your garden!
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