Bramble is the common name for the genus Rubus which includes raspberries, blackberries and their hybrids and cultivars. The term bramble is used to denote “thorniness” a common trait among these plants. This is not always the case as new varieties have been released that lack thorns. Brambles most unusual characteristic is that their root system and crown is perennial, while their canes are biennial. This means that although the plant will live for many years, fruit will only appear on canes that are two years old.
The first year a cane is produced it grows in height and develops fruit buds – these canes are called primocanes. During the second year these canes will flower, set fruit, and then die – these are call floricanes. To complicate matters, in an established bramble planting, primocanes and floricanes are growing and developing at the same time. Proper pruning of brambles not only increases fruit production but helps to make the mass of canes easier to manage.
Brambles are classified as erect, semi-erect, and trailing based on their growth habits. As semi-erect and trailing varieties require detail information on trellises and training. This article will focus on pruning techniques for the free-standing erect varieties of blackberries and raspberries.
Free-standing black and purple raspberries and erect blackberries are pruned very similarly as they all grow from a hill. During the dormant season (late winter to spring) prune out weaker canes and thin the remaining canes to about five or six per hill. It is also good to remove the lateral branches from the lower 12 to 18 inches of the canes to improve air circulation and ease of harvesting. The remaining laterals should be pruned to about 12 inches long for blackberries and 8 to 10 inches long for black and purple raspberries. Regardless of its length, be sure to remove all parts of the laterals showing winter injury.
All floricanes should be removed as soon as possible after harvest. During the growing season, each primocane should be pruned back using a heading cut. Heading will increase lateral branching and yield potential. Canes of erect blackberries should be headed at 48 to 60 inches; black raspberries at 24 inches; and purple raspberries at 28 to 32 inches above the ground. Don’t wait until late summer or fall for heading cuts since that will reduce fruit for next year.
Red raspberries are grown in a hedgerow. During the dormant season, you should thin these brambles to an average of 7 strong canes per linear foot of row. Although many cultivars are considered erect, a support system is recommended. In the summer after the floricanes have produced they should be removed along with any weak primocanes to maintain good light distribution through the rows. Red raspberries are not cut back like black raspberries as they do not produce side shoots as readily.
Everbearing raspberries are unique in that they bear fruit on the primocanes or first-year canes. This raspberry doesn’t fruit in the summer but instead develops a primocane that fruits on its upper part in late summer and fall. With these brambles pruning has been simplified. During the dormant season, mow the entire stand to 1 to 2 inches above the ground and remove the clippings. This technique will reduce disease carryover and result in a larger crop from the new primocanes next fall.
Proper pruning can promote growth, increase yields, improve fruit quality, and reduce pest problems. Likewise a well-trained bramble will make maintenance and harvesting easier.
— Kelly Jackson, Christian County Extension Agent