I have little experience with blackberries but from what I have read they are more adapted to our alkaline clay soil then any other berry plant. It might be that they are just getting established or there might be some other issue with the soil like too much or too little water and fertilizer? My Chester blackberry I planted last year is growing like crazy and it is in hard compacted clay soil, so I don't think that is the problem. It did take it all of last summer before it really started to grow.

I have successfully grown black berry plants in Cache Valley for about 8 years. I purchased plants from Stark Brother Nurseries (online). They are a fairly new type of blackberry that blooms on first year canes, not just second year canes. That is good for Cache Valley since mine ALWAYS winter kill. The canes die back down to the ground. Each Spring I cut off all of the dead canes and new canes grow back with a vengeance! I am harvesting them now. Besides watering them normally, I give them iron chelate (Sprint is the best) and a common all purpose garden fertilizer with all 3 elements. In fact, I plan on baking a black berry pie tonight! The berries get huge and taste so much better that the ones you buy in the stores. Here are some pics: