If the berries are packaged in containers or boxes, look them over carefully. If there are red stains on the box, the berries may be overripe and starting to decay. Fresh blueberries are generally available from May through September. Blueberries are best kept in a single layer in a moisture-proof container in the refrigerator for up to five days. Do not wash until ready to use.
Frozen berries are available throughout the year.
They are purplish to black, and range from to 1 inch long. Fresh blackberries are available May through August depending on climate. A hybrid berry created by American horticulturist Rudolph Boysen in the 1920s. Boysen crossed a blackberry and raspberry producing a very large, almost jet-black berry with the sweetness of the blackberry and tartness of the raspberry. Usually available in summer, select berries that are uniform in size and do not wash until ready to use.