How to Prune Brambles (cont)
By: Lee Reich
Upright blackberries, black raspberries, and purple raspberries. These brambles bear fruit on branches growing from canes. Stimulate branch growth by pinching out the tip of any new cane when it's about 3 feet tall. Not all canes reach that height at once, so prune the patch a few times during the summer.
Sometime during the dormant season, prune the pinched canes again, shortening all the branches back to 4 to 18 inches. This allows sturdier branches to bear more fruit.
Trailing blackberries. Cut away old canes and reduce the number of new ones. During dormancy, shorten too-long canes to about 7 feet, then shorten the side shoots to 1 to 1 1/2 feet.
Trailing blackberries are usually trained to a trellis. After pruning, allow each season's new canes to trail on the ground, where they won't crowd fruiting canes.
Alternatively, train new canes on one wire or in one direction along the trellis, and train fruiting canes along the other wire or in the other direction.
Red and yellow raspberries. Fruit stalks grow on the canes, not on branches. Therefore, once the old canes and excess young canes have been cut to the ground, shorten the canes that remain (while plants are dormant). Longer canes produce more fruit.
Canes should be shortened for two reasons: to make harvesting easier and to prevent the canes from flopping around in the wind. How much to shorten them depends on your trellising method. You can surround the rows with two rows of wire strung between posts at each end of the row at 2 and 5 feet above the ground. Either tie the canes to the wires and shorten them to about 6 feet, or leave the canes nearly full length, then bend them along and around the upper wire.
Pruning Everbearing Brambles
Prune everbearing types of red and yellow raspberries as you would prune the summerbearing kind, with one difference. The year-old canes will have started fruiting at their ends late the previous year and will finish fruiting lower down the second year. Therefore, shorten those canes to just below where they stopped fruiting the previous year. Old fruit stalks hanging on the canes show you where to cut.
A simpler way to prune these raspberries is to cut the whole planting to the ground in autumn. By doing that, however, you lose the midsummer crop, harvesting only a late-summer or fall crop. The advantages are that pests cannot overwinter in the canes, and you don't need a trellis. Also, you needn't worry about damage from winter weather or browsing deer.