Choose the planting location for the blackberries. Blackberries thrive in warm, well-ventilated areas that receive at least eight hours of full to partial sunlight. Blackberries prefer full sunlight but are intolerant to excessively hot temperatures, as this environment will cause sunburn and scalding. Heavy shade will reduce the fruit production. Good ventilation free of heavy winds will reduce the potential for disease.
Select a location that provides ample growing space. Blackberries are categorized as erect, semi-erect, and trailing. Erect blackberries will grow upright in dwarf tree form. Semi-erect blackberries are somewhat upright and require support. Trailing blackberries are runners that span across the area rather than upright.
Prepare the growing area at least one year prior to planting the blackberries. Nutrient-rich, sandy loams with pH levels resting between 6.0 and 6.5 are ideal for blackberry growth. Test the soil and make the appropriate corrections, rechecking often. Increase the soil's potassium, nitrogen and phosphorus levels with active fertilization. Remove sods and weeds from the area. Never plant blackberries where potatoes, peppers, tomatoes or eggplants have recently resided. This will help to avoid verticilium wilt.
Plant the blackberries in a hole that is large enough to support the root system. The root system should rest at least two feet under the top layer of soil. Space the erect varieties two to four feet apart to allow proper aeration. Trailing varieties require at least 6 feet between each other. Once planted, remove any foliage that rests three inches or closer to the ground to promote vigorous new growth.
Water the blackberries regularly, at least once each week, during the growing season. Blackberries are intolerant to periods of drought and compensate with immediate growth stunt and fruit reduction. Irrigate the soil thoroughly to provide moisture to at least the top six inches of soil. The plant will require at least one inch of water per week. Do not over-water.
Fertilize newly planted blackberries within 60 days of planting. The blackberries should be somewhat established and showing active growth. Use a fertilizer that contains nitrogen, phosphorus, and potassium. Fertilize blackberries twice a year, just after the first signs of bud break and again after harvest completion. Use a 30-10-10 fertilizer during the first three years and reduce to a well-balanced 10-10-10 after the third year.
Harvest the blackberries as they become ripe. Sweet, well-ripened blackberries will have a dull appearance and be firm to the touch. Pick the blackberries several times a week until the harvest is complete. Harvest the berries in the morning sun while temperatures are cool.