Is there something I can add to the soil so that the berries are not so sour?
Certified GKH Gardening Expert
The number one reason for sour blackberries is harvesting too early. If your picking them at a black glossy stage, that is too early. Allow the berries to dull some in color prior to picking. The soil PH should be around 5.5 to 6.5 for quality growth. Therefore I would not add lime or anything else unless your soil is simply too alkaline in nature.