Boysenberries are vine berries that typically grow abundantly with horizontal vines. A gardener must support the trailing vines of the boysenberry plants to ensure healthy and robust boysenberry vines. Aside from supporting the vines, the biggest job with boysenberry plants is the harvest. After harvesting a bountiful boysenberry crop, prune back the canes that bore fruit. In this way, you will prepare the plants to produce a new boysenberry crop during the next growing season.
Wait to prune boysenberry plants until you have harvested all of the ripe berries. Use the bypass pruners to remove all of the floracanes. Floracanes are the canes that bore fruit during the current growing season. Cut the floracanes down to 1 or 2 inches above the soil level.
Tie all of the primocanes onto a trellis to support them. Primocanes are the new canes that began to grow during the current growing season. Use the twine to attach the primocanes carefully to the trellis.
Remove the tips of the primocanes during the middle of the summer when the canes are approximately 3 feet long. When you "tip pinch" in this way, you remove only a few inches from the tips of the canes. This pinching encourages lateral growth in the canes.
Cut back the lateral branches from the primocanes of the previous season the following spring. Trim these lateral branches so that they are 1 foot long.