We planted a blackberry bush last Spring. It grew over the summer and, this year, is showing many berries forming. At the same time, there is a sizeable stalk, growing vertically from the base of the plant. It is just a stalk with leaves branching out – no berries. Should this stalk be left to grow or pruned because it is drawing water and nutrients away from the berries?
Sounds like it may be a sucker stem and you can remove it as it is taking energy away from the fruit production.