What you’ll need
- Pruning shears
step 1: Plant in Rows
All raspberries grow new canes one year which bear fruit the second year, then die. Black and purple raspberries have different growth habits than red raspberries, so are trained and pruned differently. Plant them 5 to 6 feet apart in rows 6 to 10 feet apart. Unlike red raspberries, which grow new canes from roots, black and purple raspberries only grow new canes from the base of old canes, so tend to remain in one spot.
You will get more berries if you build a trellis and train the canes to it, but the trellis isn’t necessary. If you build a trellis, set posts 4 feet high and 20 feet apart with cross arms 18 inches long. Run wires along the ends of the cross arms to support the canes.
step 2: Pinch the Tips
As each new cane reaches 4 feet high, prune 4 inches off its tip to force side branches to grow. Since new canes arise at different times, you will need to pinch tips about once a week, beginning in May. Stop pinching in August. Canes that start later than that are weak and will be discarded in the spring.
step 3: Remove Spent Canes
When the harvest season is finished, remove all the canes that bore fruit.
step 4: Dormant Season Pruning
In early spring, before new growth starts, remove the weakest canes to leave 4 or 5 of the strongest canes per plant. Prune back the side branches of these canes to 12 inches for black raspberries or 18 inches for purple raspberries. The side branches may be 8 feet long, so this will be a heavy pruning, but will result in larger, higher quality berries. Prop or tie the canes inside the trellis.