Seeds (true seed + endocarp, hereafter seeds) of Empetrum hermaphroditum are dormant at maturity in September and October, and fresh seeds collected at various sites in Sweden germinated to only 2-5% in light at daily alternating temperature regimes of 15/6, 20/10, and 25/15C. Dormancy was not due to impermeability of the stony endocarp surrounding each seed, and embryos did not grow prior to radicle emergence. Thus, seeds did not have physical dormancy or morphological dormancy. Long periods of cold stratification (32 wk) and of warm stratification (16 wk) given separately resulted in a maximum of only 25 and 10% germination, respectively, in light at 25/15C. After 12 wk warm stratification plus 20 wk cold stratification, however, seeds germinated to 83-93% in light at the three temperature regimes. When length of the cold stratification period was constant (e.g. 20 wk), germination increased with increase in length of the warm stratification treatment preceding cold stratification. Gibberellic acid promoted germination in a high percentage of the seeds. Based on dormancy-breaking requirements and response to gibberellic acid, seeds have intermediate physiological dormancy. In regions where summers are relatively short and cool (or if seeds become buried in soils that are cool during summer), the requirement for warm plus cold stratification to break dormancy may cause germination of a cohort of seeds to be spread over time, thus helping explain the occurrence of persistent soil seed banks in this species.

Key words: life cycle biology, plant ecology, reproductive biology, seed dormancy, seed germination