A long-living perennial plant with biennial canes, the blackberry falls into two categories: erect and trailing. Erect blackberries are cold-hardy blackberries that have stiff, arching canes. Trailing blackberries, often called dewberries, require assistance in standing and are otherwise not self-supporting.
Select an erect variation of the blackberry that is more cold-hardy and capable of surviving the harsh Michigan winters. Choose a highly elevated planting location for better air circulation and less potential of cold-weather freeze damage. Select a location that provides good protection from heavy winds and severe weather.
Plant the blackberries in a well-drained, nutrient-rich location that provides at least 6-8 hours of partially shaded to full sunlight. Ensure that the soil is loamy; consisting of fairly equal amounts of soil and organic matter such as compost, leaves or peat moss. Steer away from planting the blackberries in heavy clays or sandy soils.
Reduce the potential for fungal diseases. Avoid planting the blackberries where certain plants have been planted within the past three years. These plants include peppers, eggplant, tomatoes, potatoes, and strawberries.
Plant the blackberries in the early spring, just after the final frost. Position multiple plants approximately 3 feet apart. Dig a hole with a depth at least 1 inch deeper than its original container. Position the plant in the center of the hole and fill the hole with the soil. Press firmly to secure the plant's stability.
Feed the blackberries each spring once the growing season has begun. Do not apply fertilizer until the plant shows signs of new growth. Select a slow release, granular fertilizer with low levels of nitrogen. A 10-20-20 (NPK) combination is ideal. Distribute the fertilizer across the patch. Use a balanced fertilizer for plants that lack bloom vigor, such as a 20-20-20 combination.
Water the blackberries approximately once per week. Ensure that the plant receives at least 1 inch of water each week. Adjust the watering schedule for heavy rainfall and drought periods.
Avoid pruning the blackberry plant during the first year. Promote branching by trimming away 2 inches of the newly developed primocanes. Complete this when the primocanes reach approximately 3 feet in height during the second and subsequent mid-summers.
Remove floricanes after the harvest is complete. Thin each blackberry plant's primocanes, during the winter months, by removing all but three or four of the strongest canes. Erect a trellis on either side of the erect blackberry plant to promote upright growth.
Harvest the blackberries as they ripen. Inspect the blackberries daily and pick when the berries have reached full color and size. This will vary based on the selected variety. Complete the picking process during the early morning to early afternoon hours. Harvest the berries two to three times per week until complete. Snap the berries from the tree rather than pulling.
Inspect the blackberry plant regularly for signs of insect infestation and disease. Look for infestation signs such as aphid, webs, spider mites, nibbled or eaten foliage spots and tips. Examine carefully for signs of disease such as fruit rot, spots on foliage or cane, rusting, and scabs. Treat infestation and disease immediately. Spray the tree with a insecticide to eliminate and prevent infestations. Diagnose and treat disease immediately. Speak with a local nursery specialist for diagnosis and treatment assistance.