I bought 6 black berry bushes 3 years ago from an on line seed and plant company. I have been feeding them 13-13-13 for the past 3 years. All the bushes bloom but only 2 are producing berries and they are about the size of raisins. Any one have any ideas on what I am doing wrong and what I need to do to get berries.
Cookieg

Do you have at least 2 different varieties? You need that for pollination. In the full sun? Do you prune? I would try a fertilizer a bit lower in nitrogen. How often do you fertilize? Does the foliage look good and green and they're growing normally?

I only have one kind, I will get another this year. The foliage is nice and green but I have not pruned. I will try that this year. Thanks for your advice

Get a fertilizer for fruiting plants while you're at it.

Did you grow those from seed 3 years ago? Under-developed fruit and/or early fruit drop is often just a sign of an immature plant. Maybe you just need one more year for the plants to mature.