Blackberries are extremely soft and very perishable. Websites such as Foodfit.com suggest the immediate use of blackberries, as they tend to turn to mush when kept too long. For those looking to use blackberries in a day or two, Foodfit.com recommends storing them at room temperature or refrigerating them in a single layer to avoid them from crushing one another. To better preserve them, wait to wash the berries until just before consumption. This will keep them from softening at an even quicker rate.
Blackberries are extremely tart fruit until they have ripened to the point of falling off the bush. This is when they have lost their shine and are slightly dull in appearance. The fruit is then a sweetened tart flavor that is enjoyable in many forms. But in nature, the fruit is meant to fall off the bush and be consumed by a passing animal attracted to the berry's sweet smell.
Blackberries might not last long when left fresh, but they can be frozen for up to six months. Organic Grocery Deals' website suggests freezing blackberries in a single layer on cookie sheets before placing them in freezer bags or moisture-resistant containers. The berries should not be kept at temperatures less than zero degrees F. When needed, the blackberries should be removed from the freezer and thawed before being used immediately.