What is the difference between suckers and primocanes on blackberries?
The Blackberries produce canes in the spring called primocanes.
Suckers refer to the growth that comes up from the ground runners.
Here are some links that may help you identify the parts of the plant more easily,
Here is a site that will help you iron out the differences between primocanes (fall fruiting, tall, no lateral branching), floricanes (summer fruiting, tall, lateral branching), and suckers (non-fruiting, short spindly canes): https://www.wikihow.com/Prune-Raspberries.