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Abstract
The frost hardiness temperature (i.e., the temperature that causes damage) and the lethal temperature (i.e., the temperature that causes death) were assessed in summer (January) and winter (July) for 35 Hebe species, cultivars, and hybrids. Frost hardiness was also assessed in both autumn and spring for a limited number of these selections. The amount of frost tolerated in summer, when assessed using the frost hardiness temperature, ranged from only ‐1.5°C (H. diosmifolia (spring flowering type)) to ‐4.5°C (H. albicans, H. cupressoides, H. macrantha var. macrantha, H. odora, H. odora ’Anomala’, H. odora ’Buxifolia’, H. pimeleoides ’Graeme Paterson’, H. aff. pimeleoides, H. propinqua, H. recurva, H. topiara, H. ’Emerald Gold’, and H. X youngii) and, when assessed using lethal temperature, from ‐2.4°C (H. ’Inspiration’ ) to‐8.1 °C (H. cupressoides.). In winter the frost hardiness temperature ranged from ‐2.4°C (H. diosmifolia (spring flowering type) and H. ’Inspiration') to ‐8.1°C (H. cupressoides) and the lethal temperature ranged from ‐4.5°C (H. diosmifolia (spring flowering type), H. elliptica var. elliptica and H. ’Inspiration') to ‐12.9°C (H. cupressoides and H. propinqua). We present information on hardiness levels that challenges the current classification of some of the material based on hardiness zones.