Blackberries are at their peak in June in the southern United States. In the north, they ripen a little later, in July. Ripening is dependent on the weather.
Ripe blackberries are deep purplish-black in color, with no signs of red. They will be plump and juicy, and will easily pull away from the plant.
When picking blackberries, wear jeans and a heavy, long-sleeved shirt to protect the skin from thorns. Loose clothing will snag on the plants.
Blackberries will keep in the refrigerator for up to a week, but are best when eaten fresh. Blackberries left at room temperature will mold quickly, so plan to use or freeze blackberries right away.
To freeze fresh blackberries, wash and place them in a plastic bag. Freeze. Blackberries will keep for several months in the freezer.