Last year I planted one blackberry bush. This year we got three berries and that is all. Do I need to plant another blackberry bush for cross pollination?
Two Blackberry Bushes for Cross Pollination
Certified GKH Gardening Expert
While most blackberry bushes are self-fertile, a few cultivars work better when planted near another variety of blackberry.
This article will help wtih growing blackberry plants: https://www.gardeningknowhow.com/edible/fruits/blackberries/growing-blackberry-bushes.htm