Freezing Survival of ‘Illini Hardy’ Blackberry Floral Tissues Before and After Budbreak

Abstract

Dormant floral buds and inflorescences of ‘Illini Hardy’ blackberry ( Rubussp.) plants were subjected to controlled freezing tests. The susceptibility of dormant floral buds to low temperatures was determined by differential thermal analyses (DTA) and the hardiness of individual flowers at various stages of development was determined by viability testing. The mean temperature at which all low temperature exotherms (LTEs) were detected in primary buds was -15.0, -18.4, and -13.8°C in November, January, and March, respectively. The mean LTE temperature for secondary buds was -24.8°C in January and -18.9°C in March, indicating that secondary buds could provide a replacement crop when the primary bud was injured. After budbreak, inflorescences deacclimated as bloom progressed. When the flowers were at tight bud, the temperature range in which all flowers in the inflorescence were injured was 1.6°C. However, when the terminal flower was at full bloom or at a later stage of development, the critical temperature range was ≤ 0.3°C.