Answers are grounded in this paper and cite their sources.
Hardiness of intact roots of Potentilla fruiticosa L. cv. Katharine Dykes and Picea glauca Voss were determined during the autumn. Both extended photoperiod and warm temperature interfered with root acclimation to cold. Seasonally short days and near freezing temperature were necessary for maximum rates of cold acclimation of roots.
No takes yet. Share an insight, caveat, or question.
Johnson et al. (1977) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: