When rainfall doesn't provide this amount, you should irrigate. Extremely warm and windy conditions make greater amounts of water necessary. A good guide for fertilization is to observe plant growth. Canes should grow well and be stout rather than spindly. How you should prune erect and trailing blackberries varies slightly.
All cultivars require very little pruning or training during the planting year.
In the summer, remove the top 1 to 2 inches of new primocanes when they're 3 feet tall. This causes canes to branch, and these branches will produce fruit the next year. In late winter, when plants are dormant, thin primocanes to three or four of the strongest canes per plant. If you have plants growing in a hedgerow, thin to one large cane every 5 inches in the row. Prune lateral branches on these canes to 12 to 18 inches long.