Blackberries are one of the easiest fruits to grow in the home garden. A properly planted and maintained bed of blackberries will continue to produce for 15 to 20 years. Blackberries are available in trailing or upright varieties, with the upright varieties more winter hardy than the trailing ones. Thornless varieties are also available, but these are less hardy than varieties with thorns. Blackberries ripen in mid-summer, approximately 60 to 70 days after their flowers bloom.
Pick a spot to plant blackberries in your garden that receives sun at least 8 to 10 hours a day (more is better). The soil can be sandy or clay but should be well-drained. Do not plant blackberries in the same spot where potatoes, peppers or tomatoes have grown for the previous five years. All of these plants are susceptible to verticillium wilt, which may linger in the soil for several years and infect blackberries, which are also susceptible to verticillium wilt.
Provide a means to support the blackberries. They can be planted next to a fence or an existing trellis. Or you can erect a trellis consisting of support posts at either end of the row with heavy gauge wire attached to each post 2 feet above the ground and strung along the row. Similarly attach another wire to each post approximately 3½ feet above the ground.
Prepare the soil. Add 2 to 6 inches of compost and 2 inches of peat moss to the surface of the soil in the planting bed. Dig or rototill the soil to incorporate these amendments. Rake the bed smooth.
Remove any broken roots from the bare-root blackberry transplants. Soak their roots in a bucket of water for about 1 hour to re-hydrate and keep them from drying out while preparing the planting bed.
Dig a hole that is approximately the same diameter as the spread of the roots of the individual plants. Space upright varieties of blackberries 2 to 4 feet apart in rows 8 to 10 feet apart. Space trailing varieties of blackberries 8 to 10 feet apart in rows that are also 8 to 10 feet apart.
Spread out the roots of bare-root blackberry plants in the planting hole. Back fill with soil and firm the surface with your foot. If planting container-grown blackberries, sever the roots that encircle the root ball to encourage them to grow outward from the center of the plant. Ensure that the plants are set in their new home at the same level that they were growing before transplanting.
Make a ridge with your hands around the perimeter of the planting hole. This will create a saucer-shaped depression that will help rainwater find the roots of the plants rather than running off into the spaces between the plants.
Put a soaker hose in the row next to the newly planted blackberries and allow it to thoroughly water them. Thereafter, provide blackberries with the equivalent of 1 to 2 inches of rainfall per week.
Mulch around and between the plants and in the rows between them. Use 6 to 10 inches of straw or hay. The mulch will keep the soil moisture relatively stable and discourage the growth of weeds.
Feed blackberries by spreading slow-release 10-10-10 granulated fertilizer at the rate of 2 pounds for every 100 feet of row in early spring and again after harvesting for the first two years after planting. Thereafter, use 4 pounds of the same fertilizer for every 100 feet of row.