Fruit or crops being ripe actually implies its being fully grown and ready to eat. It is however often hard to distinguish between fruit that is ripe and the one which is still not fully developed and not appropriate for consumption. Fruit goes through a number of changes as it ripens which have an intense impact on its taste and look. When undergoing the ripening processes, fruit is growing sweet, less tart and sour, it also gets more succulent, of more intense color, and begins to produce a strong aroma. Some sorts of fruit can develop off the parent plant (bananas, peaches, plums, apples, melons), while others are not able to ripen off the parent plant, since they have to be necessarily vine or tree ripened. Based on the type of fruit, there are several common rules which can be employed to discern a perfectly ripe fruit.
First of all, most fruits are never green when ripe. This is typical for most citrus fruits, also including bananas, apples, pears, pineapples, mangos, etc. When being ripe they generally take on yellow or orange color. There are some exceptions to the rule however. For instance avocado and some sorts of melon are edible and sometimes even green when ripe. Still, green is not often the last phase of ripening.
Secondly, fruits usually start to shine as if waxed when being ripe. This feature is characteristic for citrus fruits, cherries, and to some degree for apples. However it wouldn’t be out of place to mention that many producers these days really wax their fruits to make them look healthier and to protect them from possible external harmful factors.
Furthermore, fruits get softer when ripening. If a fruit stands firm even if being pressed softly, it generally means it fails to be ripe. This rule is not universal, however. There are some fruits that remain firm even when being exquisitely sweet. There are several levels of firmness, so it is necessary to distinguish between an excessively rigid and a normally resilient fruit.
The last but not the least, ripe fruit typically emit a luscious scent. Unfortunately, aroma is not a very helpful indicator in practice, since it can only be smelt at room temperature, while most fruits are sold colder than they naturally are. Moreover, there are some fruits whose scent never fully develops, since their aroma composition comes from the plant they grow on (kiwis, mangoes, papayas, cherimoyas) and of which they are usually separated before fully ripened.