Blackberries are among the favorite fruits of berry lovers. They also are the easiest to grow from seeds. Growing blackberries from seeds takes a few different steps than growing other types of fruit from seeds, such as apples or pears. Blackberries, once properly started and planted, can produce fruit for many years from the same vines.
Pick ripe berries to start. These will provide the best seeds from which to grow your blackberries. Place the berries in the strainer. Press the pulp so it separates from the seeds. Wash the seeds clear of the rest of the berries. The seeds will remain in the strainer.
Wrap the seeds in damp peat moss. Place the seeds in a plastic food storage bag and seal. Place the bag into the refrigerator but not in the rear as this could cause freezing. Keep the seeds in the refrigerator for four weeks at the start of winter.
Remove the seeds from the refrigerator and peat moss six to eight weeks before the last frost of winter. Fill plastic cups half way with potting soil. Sow the seeds in the soil and place the cups along windowsills. Keep the cups in windows, which will allow a temperature range of about 70 degrees Fahrenheit. Water the seeds with 1 inch of water per week.
Start looking for a permanent location for the blackberries when the seeds begin to sprout. You will have about four weeks to locate suitable ground. Blackberries need well-drained soil and can handle alkaline soils.
Plan to place the blackberry vines away from other gardens or paths. These vines need room to grow and can overtake areas quickly. Plan to place the seedlings 2 feet apart and the rows 7 feet apart from each other.
Plant the seedlings when the soil is warm. Dig a large enough hole so you do not bend the roots when planting the seedlings. Trim the canes so new growth can occur. Water the plants with 1 inch of water each week. Put mulch around the plants so they don't dry out. Spread 10-10-10 fertilizer around the plant base in mid and late spring.
Set trellises behind the plants during the first year so the vines grow up the trellis. Continue to cut off suckers outside of the rows and prune out some canes to strengthen the remaining plant and berries.
Continue pruning in the second year by removing branches where you already harvested berries. Prune these branches back to ground level. Thin the remaining branches to four canes per foot per row. Cut fruit-producing canes to the ground in the late fall to ensure the next year's crop.