Sometimes called erect blackberries, cane blackberries do not trail or vine. To keep cane blackberries healthy and productive, the home gardener should plan on pruning the blackberries several times a year, targeting different types of cane. Both pruning and spacing promote air circulation, which makes it less likely for the blackberry crop to develop a fungal or bacterial disease. If not tended carefully, a blackberry patch can invade other parts of the garden.
Plant blackberry bushes 4 to 6 feet apart in a row, as early in the spring as you can work the soil. If you're planting multiple rows, leave 8 to 10 feet between rows.
Blackberries produce vegetative shoots called primocanes during their first year. In the second year, primocanes mature into floricanes (which produce berries) and the blackberry grows new primocanes. Let the plant grow until mid summer.
Trim primocanes back to a height of 48 inches in June or July with anvil pruners. This encourages branching, increasing the berry crop for the following year.
Wait until the end of the growing season to prune again. Harvest any berries that were produced on floricanes. Then cut off the floricanes at their base using anvil pruners.
Leave the blackberry plant alone until early spring, when frost danger has passed for your area, but the plant has not begun growing again. At this time, trim the lateral shoots of your primocanes back to a height of 18 inches. Prune away weaker-looking primocanes. Oregon State University suggests leaving three to four primocanes per berry plant.
This thinning prevents crowding, which can lead to fruit rot and poorer-quality fruit.
Continue to prune your blackberry bushes on this schedule to maintain optimum plant health and fruit quality.