Answer: All raspberries benefit from some type of support system because canes are susceptible to wind whipping, particularly when the fruit is present. Such a system can be as simple as posts with twine tied between them, or more elaborate with permanent posts and wire.
With the narrow hedgerow system, the simplest trellis system uses single or double wires or twine. Place posts about every 10 to 12 feet. Then place the canes between the wires and tie them loosely to the wire. The wires can be tied every 2 feet to prevent spreading. Remember, the rows need to be kept narrow.
Black and purple raspberries grown in the hill system need to have a support system as described above. The only difference is that there are no primocanes coming up between plants so canes need to be tied along the wire to fill the trellis.
Raspberries grow vigorously and need to be pruned yearly. Pruning practices depend on the type of raspberry grown.
Summer-bearing red and yellow raspberries: After the last harvest, cut all canes that have produced fruit to ground level and remove them. This eliminates a disease source and gives primocanes more room to grow. Thin primocanes to 4 to 5 sturdy canes per foot of row. In areas where winter injury is common, delay thinning primocanes until the following spring, however primocane growth will be less because of the competition among canes. Before growth starts in spring, cutting the canes to about 12 inches above the wire is desirable. Never cut more than 25% of the cane since this will begin to adversely effect yield.
Fall-bearing raspberries: If only a fall crop is desired, cut all canes off at the base before growth begins in spring. Fruit will be produced on primocanes in the fall of the year. If a fall and summer crop is desired, thin the canes as described for summer-bearing raspberries. The primocanes that produced the fall crop should not be removed as they will produce fruit the following summer. Prune them back in spring to about 12 inches above the wire, or to the last visible node that had fruit.
Black and purple raspberries: When primocanes are between 24 to 30 inches in height, pinch out the tip of each shoot to induce branching. This will make the fruit easier to pick and increase production. After harvest, cut down all canes that bore fruit to ground level. Before growth begins the following spring, cut back all side branches to 12 - 18 inches. Select 4 to 5 canes per hill and prune out the rest. Tie these canes to the support system.
Best wishes with your raspberries!
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