Pineapple guava, also called feijoa, is a tropical fruit that grows on evergreen shrubs. The time it takes for the tree to flower and the fruit to ripen varies widely, depending on location. For example, New Zealand varieties typically bear fruit from February to May. In northern California, though, the fruit ripens in late fall or early winter. The fruit typically falls from the tree when it is ripe, although it can be harvested by hand. Once the fruit is picked, however, it's ripening process ends.
Check the fruit on the tree and on the ground for a uniform green color, suggests Louisiana State University Ag Center. The fruit's green color is one indication of its ripeness.
Pick from the tree a feijoa that you suspect may be fully ripened. If it releases easily from the stem, it is ready for harvest.
Cut one of the harvested fruits in half to see if the batch is ripe. A fully ripened pineapple guava will have clear-colored jellied sections. If the jelly sections are white or only partially clear, they fruit is not ripe. If they are brownish in color, they are over-ripe.