Kumquats are usually at their peak of quality when they become fully orange but can be eaten somewhat earlier if you enjoy a tarter fruit. Harvesting Small Fruits Determining when to harvest small fruits is usually less difficult than determining when to harvest most tree fruit. For example, blueberries should not be harvested until at least 3 to 5 days after the fruit turns blue. Unlike most small fruits, blueberries will hang on the plant for at least a week after becoming ripe and still retain necessary firmness and quality for harvest and handling. Blueberries do not improve in flavor after picking.
Harvest can begin when tasting indicates that acceptable flavor has been reached.
Blueberries do not usually have fruit-rot problems in the field and can be harvested once a week. Blackberries usually go from green to red in 1 to 3 days and red to black in 1 to 2 days. They can be picked when they turn black, but for optimum flavor, they need 1 to 3 additional days for fruits to complete swell and flavor development. Rots are a problem, so harvests should be prompt and frequent. Color break and taste should generally be used in determining when to harvest grapes.