Freeze Damage in Red Raspberries and Blackberries

Bruce Bordelon, Professor, Department of Horticulture and Landscape Architecture, Purdue University

The weather this spring has been a bit like a roller coaster ride. After a mild winter, we had a very warm February, one of the warmest on record. March, however, has been more normal with several freeze events. This has many gardeners concerned about potential damage to plants. Damage to early blooming Forsythia and daffodils is obvious following a hard freeze in mid-March. Less obvious is damage to some of our fruiting plants, particularly red raspberries and black berries.

Red raspberries, in particular, have a fairly short chilling requirement and respond quickly to warm spring temperatures. Many cultivars had visible growth in February. While the growth slowed considerable with the return to more seasonal temperatures in March, some damage has been done. Figure 1 shows buds on Heritage red raspberry at the ¾ to 1-inch stage. The leaves were damaged by the cold temperatures in mid-March. But we can’t tell from the outside leaves whether the growing point was killed. Figure 2 is an excised bud, showing the dead growing point inside the buds (black center). It is important to note that multiple buds occur on raspberries, as can be seen in the pictures. The most developed bud is damaged more than the secondary buds. It is possible that they will grow and produce a crop this season. Less developed buds such as in Figure 3 suffered less damage and appear to be healthy inside (Figure 4).

Blackberries vary in damage. Early cultivars such as Natchez have ¾ inch shoots and excising the buds shows that they are damaged (Figure 5 and 6). Apache, on the other hand, is a later cultivar and its buds developed more slowly. They are green and healthy (Figure 7). As with raspberries, blackberries can have multiple buds so there is a chance for a crop this year even if some damage has occurred.

Hopefully we will not experience any additional hard freezes for the rest of the year and fruit crops will suffer no more damage.