Heat stress in raspberries, part 1

Severe leaf cupping

Moderate leaf cupping

Today in North Carolina, the temperatures are expected to reach 99F (37C). This type of heat is extremely stressful for raspberry plants and very often they will not live for more than a year or two under these conditions. However, we have found that by screening plants in this type of environment, we are able to find some plants that are somewhat tolerant of heat.

Above are pictures of 2 plants in a seedling population taken on the same day last week when it was hot like it is today. The plants are from the same parents, and are in fact, adjacent to one in another in the field at the Sandhills Research Station in Jackson Springs, NC.  The leaves on the first plant are cupped upward, a classic sign of heat stress, while the second plant has leaves that are only moderately cupped. Most of the plants in this population had severely cupped leaves. But a few did not and those are the ones that we will keep, and test in future trials.