Frost Hardiness of Erica and Calluna

Abstract

Frost resistance of Erica and Calluna which are native to Europe and South Africa was investigated at the Gotemba Branch of the Shizuoka Agricultural Experiment Station located in a high altitude cool region of Shizuoka Prefecture. The Erica and Calluna plants introduced from Europe were overwintering in the experimental field. The Plants of both the genera from South Africa and Europe were planted in the pots arranged in a greenhouse whose daily minimum air temperature was kept within a range from 3 to 5°C.
Dormant twigs of those plants were collected in late January, transferred to Sapporo, Hokkaido and then precooled to harden for 15 days at temperatures from -1 to -3°C. Frost resistance of the dormant twigs was examined after they had acquired hardiness fully.
Most Erica plants introduced from Europe survived freezing temperatures from -15 to -20°C, while Calluna from Europe survived temperatures as low as near -30°C. On the other hand, most Erica plants introduced from the south-western Cape district, South Africa, hardly survived freezing temperatures of -5 to -8°C. Erica cerinthoides which is distributed widely in South Africa showed the greatest hardiness of all the species tested. It seems practically feasible and meaningful to set up a project aiming at selecting hardier Erica plants among those collected from different localities with various climatic conditions throughout South Africa. Physiological characteristics pertaining to plant hardiness are discussed in the present paper with reference to geographical distribution of species in question.