Brambles - Production Management and Marketing

Bulletin 782-99

Chapter 3 Selection and Care of Plants

Black, Purple Raspberries, and Blackberries

Summer Heading (Tipping)

If shoots of these plants are allowed to grow unchecked, they get long and are very difficult to manage without support of some kind. To prevent this, the tips of new canes should be pinched off (headed) when the canes have reached a certain height (Figure 13). This induces growth of side branches and results in plants that are stocky and self-supporting and have a large amount of bearing wood.

Figure 13. Remove three to four inches of top growth.

Black raspberry shoots should be tipped when canes reach about 28 to 30 inches (Figure 14). Brandywine purple raspberries are usually tipped about 36 inches. Erect blackberries are permitted to grow to a height of about three feet before tipping. Generally, plant height will be less than two feet for the planting year. Therefore, heading is done every year from the second season. Royalty purple raspberries do not require heading, because their growth is similar to red raspberries.

Figure 14. Heading or summer pruning of black and purple raspberries. Black raspberries are headed at 28 to 30 inches and purples at 36 inches.

In heading, the usual practice is to remove four inches of the top. It is necessary to go over the planting several times, because all shoots do not reach the same height at the same time. If shoots are permitted to grow much above the desired height and then headed, the extra shoot growth is wasted, and the side branches will not be as strong as if heading had been done at the proper time. The laterals should not be shortened until the following spring.

In most cases, the laterals mature sufficiently well and are not winter-killed to an extent that yields are lowered. Canes that do not reach the height for tipping by the time harvesting is started are usually not tipped. These weak canes will not grow much higher, and late tipping results in weak, immature laterals.

Removal of Canes After Fruiting

After fruiting, canes die and should be removed in March. The considerations for removing canes mentioned under Red Raspberries apply to these crops as well.

Thinning Canes

As in red raspberries, surplus blackberry canes should be thinned out in the spring. Retain strong canes, spaced six to eight inches apart. Rows should not be much wider at the base than 18 to 24 inches or picking will be difficult.

Because black and purple raspberries do not produce suckers, the canes are located in clusters or "hills" where the original plants are set instead of being distributed all over the row. Remove canes less than half an inch in diameter at the base in the spring. Usually, no further thinning is needed as plants should be able to support as many vigorous canes as they produce. Because yields depend on the number of strong canes, conditions should be made favorable enough so that from four to six strong canes are produced per hill.

Heading Back Laterals

The laterals or branches produced as a result of summer tipping may grow quite long (three feet or more) (Figure 15). Most of the buds on the laterals are fruit buds. If all were left, there would be so much competition for water and nutrients that fruit size would be small. Therefore, laterals must be headed back to thin the fruit crop. Head back laterals in the early spring after the extent of winter injury can be determined but before the buds swell and grow.

Figure 15. Black and purple raspberries before and after dormant pruning.

Blackberries

Pruning

With black raspberries, eight to 10 buds (eight- to 12-inches long) per lateral are usually enough. Purple raspberries are somewhat more vigorous than blacks, and a few more buds per lateral can be left. The length of laterals in both purple and black raspberries can be increased somewhat if canes have only two to three laterals and if there are only a few canes per hill or when irrigation is available.

Erect blackberry cultivars differ in their fruiting habits. In some cultivars, the fruit clusters occur well out on the laterals; in others, they are close to the main stem, and in others they are well distributed over the lateral. Generally, at least half of each lateral may be removed. The erect blackberry should be handled similar to the black raspberry.

Thornless blackberries that have not been damaged by cold temperatures need to have all laterals removed within 18 to 24 inches of the soil (Figure 16). These low-positioned laterals will produce fruit that will not be harvested or will be covered with soil. Next, head all laterals back to 12 to 18 inches. If the main shoot is excessively long, it can be cut back to give space to other plants. Thin out small diameter canes and leave four to six canes per plant. If the thornless blackberries have been damaged by cold temperatures, remove all dead wood. If there are only three or four laterals that show signs of life, these may be headed back to three to four feet after being tied to the first wire of the trellis.

Figure 16. Thornless blackberries before and after dormant pruning.

It may be advisable to summer prune or head back thornless blackberries. Summer pruning may stiffen canes, create vigorous laterals near the pruning cut, and may be helpful under heavy snowfall. A strong trellis will be necessary under heavy fruiting.