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- Prune Blackberries in Summer for Best Results
Summer pruning of blackberries is an important management tool. It is helpful in fruit harvesting, controlling insects and controlling diseases, according to LSU AgCenter horticulturist Dr. John Pyzner.
Two basic types of blackberries are erect and trailing. Erect blackberries have an arched self-supporting cane. Trailing blackberries have canes that are not self-supporting and must be placed on a trellis for support. Trailing types are often called dewberries. Pruning procedure varies with the different types of blackberries.
Blackberry canes are biennial, living for two years. Blackberries send up new shoots (primocanes) from crown or buds formed on the roots. These canes produce no flowers or fruit the first year. The second year these canes are called floricanes. These are the canes that flower and produce fruit.
Floricanes gradually die after fruiting. Old floricanes should be removed and burned immediately after fruiting, usually late June or early July in Louisiana.
Pyzner recommends severe summer pruning on varieties that are highly susceptible to rosette disease and are located in areas where rosette disease is prevalent.
The horticulturist says that removing the new primocanes with the old floricanes immediately after harvest eliminates spring rosette infections in the primocanes. One way to do this is to mow all the canes to the ground.
Apply fertilizer immediately after harvest as a band on both sides of the row at a rate of one cup of ammonium nitrate or three cups of 13-13-13 fertilizer per 24 feet. of row. Fertilizing will force new cane growth.
New primocanes should be topped in the summer when they reach a height of 3 to 4 feet. Growers will need to top the canes throughout the season since the canes emerge at different times. Topping the primocanes in the summer promotes self-supporting plants and encourages lateral branch development, which increases fruit production the following year.
Select four to six canes per lineal foot of row for next year’s fruiting wood. Cut lateral branches back to about 12 inches before growth starts in the spring.
Prune trailing blackberries by selecting the best four to eight canes and tying them to supports. Remove extra primocanes and old fruiting canes.