Blackberries grow best in sandy loam soil. Otherwise, they can be grown in soils that are at least one-foot-deep, have good drainage, and have a pH between 4.5 and 7.5. Organic amendment (compost) should be added at planting time. On soils with a pH of 8.0 or above, soil sulfur may be incorporated into the soil before planting or when thinning canes. Otherwise, plants may experience zinc or iron deficiency and applications of zinc sulfate or iron chelate may be necessary. If soil drainage is inadequate, grow blackberries in a raised bed filled with mineral soil. They perform best in full sun when grown at elevations above 2,500 ft.
Blossoms may be damaged at temperatures below 26 degrees F and drying winds can damage canes between 20 and 24 degrees F. For this reason, select a wind-protected location.
Both erect and trailing blackberries should be trained to a trellis. Trellises for trailing varieties are constructed by stretching two wires (3 and 5 feet above ground level) between steel or rot-resistant wooden posts. Erect varieties may be adequately staked with one wire 3 feet above the soil. End posts will need to be strong and well anchored.
Proper pruning is essential for good production. Erect varieties should be topped at 3 feet during the first summer. This encourages lateral branching, which is where the fruit will be produced the following year. These laterals should be pruned to 12 inches the following spring. Erect varieties should be thinned to 5 or 6 strong canes per foot of row in the spring. Trailing varieties should be thinned to 6 to 12 strong canes per foot of row and trained to the trellis wires in spring. For both trailing and erect varieties, old canes that have produced fruit the previous year should be removed after they have died back.
Nitrogen is the most critical nutrient for blackberry production. Apply from 1 to 1 ½ oz. N per plant (6 to 10 oz. 16-16-16 per plant) per year. Weekly irrigation should be applied by flood, furrow, drip, or other method that wets the soil to a depth of 1 foot. Sandy soils may require more frequent irrigation. Avoid aerial sprinklers that wet foliage as this could promote disease. I have included a link to additional resources below. Enjoy your blackberries!