2017 ASHS Annual Conference

Cornus mas (Cornelian cherry) is a deciduous shrub or small tree that is native to southeastern Europe and western Asia. It is unique among the Cornaceae (dogwood) family in that the fruit is highly nutritious and contains high amounts of antioxidants and anthocyanins. While this plant has many desirable fruiting and ornamental characteristics, it has seen limited use in North America. Several of these desirable characteristics are low disease and pest incidence, fruit qualities, and early yet long-lasting flowers. Little is known about the cold hardiness of this species being that there has been limited use outside of its native range. This study aims to determine if controlled freezing can be used to analyze potential hardiness of different cultivars to select for northern zone field trials. To do this, five cultivars (‘Flava’, ‘Golden Glory’, ‘Pyramidalis’, ‘Spring Glow’, and ‘Variegata’), one variety (var. elegantissima), and one individual (TS79239, established at the NDSU Research Arboretum near Absaraka, North Dakota, USA; Lat: 46.9859, Long: -97.3549) were exposed to five temperatures (-24, -32, -36, -40, and -44 °C) using a controlled freezing chamber. Stem tissue was evaluated for all selections and additional flower buds and vegetative buds were evaluated for the Absaraka selection. Electrical conductivity (EC) was recorded for each tissue sample after exposure to freezing treatment temperatures and heat killed temperature. This gives a percentage of the number of ions that were released after freezing and therefore how much damage was done at each temperature. Test results showed ‘Variegata’ to have nearly 70% tissue damage at -24, -32, and -36 °C and then increase to 80% damage at -40 and -44 °C. This was the most amount of electrolyte leakage for all of the selections tested. Even at -24 °C, ‘Variegata’ shows significant tissue damage that would cause extensive die-back. Stem die-back of ‘Variegata’ has been observed at the University of Wisconsin-Madison Arboretum (Madison, WI, USA; lat: 43.0419, long: -89.4297) which is located in USDA hardiness zone 5a. This study showed a gradual increase in tissue damage for the selections, however all besides ‘Variegata’ showed potential hardiness prior to -40 °C. Of the selections tested, ‘Spring Glow’ showed the best potential for hardiness in northern USDA hardiness zones. It can be concluded from this study that controlled freezing is a viable resource for determining potential hardiness for Cornus mas.