It is best to pick blueberries by gently rolling each one from the cluster with the thumb into the palm of the hand. When picking is done this way, the berries that aren't ripe will not come loose. Harvest at weekly intervals. They should be picked when they are of maximum size and full-flavored. Cherries picked before they are fully mature will not ripen off the tree.
Sweet cherries become firm when ripe, and sour cherries part easily from the stem.
Cherries that are to be shipped will keep longer if the stems are left attached. For immediate use, they can be picked with or without the stems. For making jam and jelly, however, pick them when they are firm but not fully ripe. Pectin content is high at this stage. To harvest currants, twist the cluster off of the branch first, then strip the berries from the cluster.