The thornless blackberry plant is a biennial bramble hardy in USDA growing zones 5 through 10. Blackberry plants are low maintenance but require a pruning schedule to maintain fruit production as the berries grow on 2-year-old canes. Planting blackberries in the appropriate environment and providing adequate care will produce plants that live up to 15 years of age with years three through eight being the top production years. Thornless varieties include Arapaho, Hull, Navaho and Triple Crown.
Choose a planting location for the thornless blackberries. The plant requires a well-draining soil, full sunlight and good air circulation. A sandy soil with a 2 to 4 percent organic matter is preferred.
Contact the County University Extension office for a complete soil test. The results will list the soil pH and organic content.
Remove all vegetative growth and rocks from the planting area. Work the soil to a depth of 10 inches with a rotary tiller.
Amend the soil if the pH value is not 5.0 to 7.0. Work ground rock sulfur into the soil to lower the pH number or limestone to raise the pH number. Water the soil well and let it rest for two weeks before planting.
Till 3 to 4 inches of organic compost into the planting area. Dig a 3-inch deep hole with a width large enough to fit the spread of the blackberry cane roots. Set the plant into the hole, gently spread the roots out and fill the hole with soil. Space the blackberry plants 3 feet apart in rows that are set 8 feet apart.
Apply a generous soaking of water after planting. Water blackberry plants at least twice a week with 1 inch of water to keep the soil moist during the growing season.
Prune the thornless blackberry canes to a height of 4 inches immediately after planting. This will stimulate strong cane growth.
Apply 3 to 4 inches of organic straw or pine bark mulch around the canes. This will prevent excessive weed growth and increase soil moisture retention.