Our blackberries had lots of blossoms this spring but really didn't fruit much. This spring there were more blossoms than we have ever seen before. We were really looking forward to a bumper crop, but have hardly gotten any fruit. They look very healthy. We had a wet spring, followed by a humid and hot July and then we have been dry for a 4 week period. We have never fertilized them and they have been in the ground for 4 years. Thanks.
More Blackberry Blossoms Than Fruit
Certified GKH Gardening Expert
This normally happens due to pollination issues. Very wet weather or very hot weather (which you had both of) can affect pollination. These articles will help with attracting more pollinators to your garden, which turns those blossoms into fruit: