Proper spacing and pruning is essential in maintaining healthy, productive
In dense plantings, canes compete for light. This competition influences many factors of growth, such as cane height, and thereby productivity. For many growers, control of Spotted Winged Drosophila (SWD) has driven the focus on canopy management.
Ensuring proper in-row and aisle spacing, trellising plants, and maintaining cane density and vegetative growth will optimize yields, increase picking efficacy, and increase light penetration and air circulation, which can reduce pest and disease pressure. Lower cane density is also noted for increasing fruit size and quality, as well as increasing lateral length in floricane production. Optimal cane density and pruning heights vary based on a grower’s location, production methods, trellising, and variety but this article will review our recommended best practices.
Red and Yellow Raspberries
Optimal cane density for in-ground red raspberry production is to maintain 6 – 8 primocanes per linear foot of row and then to reduce to 3 – 5 canes per foot. Cut canes to 6” above the top trellis wire, or about 4.5’– 5’, in late fall. Double cropping varieties should be cut back two nodes below primocane fruiting in late fall. Excess canes, reduce fruit size and marketability, and increases disease pressure due to reduced air circulation and light penetration. Removal of growth, from lower 12” – 18” of canes, which generally produce poorer quality fruit, in the spring increases light penetration for new primocane growth improving early growth.
While there is no standard density for primocane raspberry production, growers are now focused on control of SWD. Keeping 6 – 8 canes per linear foot of row provides a good balance of berry size and overall yield and improves control of SWD. As SWD prefers to harbor in the lower canopy, removing foliage from lower 12” – 18” of canes in mid-summer reduces the preferred habitat and increases exposure to predators and pesticide applications. Lateral growth during the primocane season is generally limited due to apical dominance.
For floricane black raspberries, keeping 6 – 8 primocanes per plant/hill and then limiting to 4 – 6 canes for in late fall is recommended. Primocanes are tipped about 6” above the top trellis wire, or about 5’ – 6’. This tipping causes lateral buds to begin growing. Prune laterals to 3” – 5” in late fall. It is important to keep laterals intact throughout the season and prevent them from contacting the soil, tip rooting. Cutting laterals during the growing season causes buds on laterals to grow, increasing canopy density and disease pressure and reducing berry size and quality.
In primocane production, timing and height of tipping highly influences yield and fruiting time. Primocanes should be tipped in early summer once they have reached 3’ in height. Tipping increases lateral growth and thereby productive space but delays harvest. Growers looking to also produce a floricane crop should cut laterals back two nodes below primocane fruiting in late fall. Double cropping should not be done until plants are at least 2 – 3 years old.
Recommended cane density and pruning for floricane blackberries on a standard trellis follows the same guidelines as black raspberries. When grown on the RCA trellis, blackberries should be maintained at 2 – 5 canes per plant, depending on the variety. Additional canes are not kept due to increased canopy density. Primocanes are trained horizontally to a low wire, about 16”. When the cane reaches the next plant, they are tipped, and foliage is removed. Laterals are then trained vertically, leaving about 3” – 5” of space between them. It is important to remove any laterals growing below the bottom wire. This will assist in maintenance of new primocanes and increase air circulation and light penetration around the base of the plants.
For primocane blackberry production, canes should be tipped when they reach 12” – 15”. Laterals should then be tipped once they reach a length of 30”. This double tipping helps to balance between increasing productive space and reducing the delay of harvest. This is necessary in the North due to the shortened growing season, however even using this method there is often an abundance of green fruit left unharvested at frost. The use of row cover in the spring to induce earlier primocane emergence and growth in high tunnels can help to increase growth and extend harvest season and therefore yield.