Seeds of many Viburnum species have epicotyl dormancy, but little is known about the temperature requirements for radicle and shoot emergennce. Chien et al. incubate fresh and pre-treated seeds of V. betulifolium and V. parvifolium under various temperature regimes and find that warm stratification is required to break the first part of physiological dormancy (PD), allowing embryo growth and subsequent radicle emergence. Cold stratification is not required for differentiation of the epicotyl–plumule, but is required to break the second part of PD, allowing the shoot to emerge in spring.
