You may be picking them too soon.
When I was a girl, my grandmother taught me that to find the sweet ones,
they had to nearly fall off in your hand when you gave them a little tug.
Try waiting a little longer, and see how it goes.
:I just planted 3 varieties of blackberries in my garden. Apache, Arapahoe
: and Rosenburgh. The only one that is producing any berries is Rosenbergh,
: but they seem too sour. They get full sun, are in soil lightened with
: and a little sand, and get adequate water. The plants are beautiful, as
: the berries. Is there some soil amendment I can add to sweeten the