A proportion of sound seeds of conifer species do not germinate during certain periods of the year, even when conditions are favorable. Mamonov et al. (1986) report that the non-germinating seeds have apparently undergone physiological changes that affected germination. This phenomenon may be due to seasonal periodicity, or biorhythms. As early as the mid-1930's, Baldwin (1935) reported seasonal variation in the germination of red spruce (Picea rubens Sarg.) seeds. David (1951) and Shomer-llan (1964) also found seasonal trends in the seed viability of several pine species. In these latter two studies, germinative capacity was at a maximum in April and May and decreased to a minimum in November and December.
Barnett, James P.; Marnonov, N.I. 1989. Biorhythms in conifer seed germination during extended storage. Ann. Sci. For. 46 sum., 85s-88s