Effect of overwinter hydration, seed storage time, temperature, and photoperiod on germination of some Carex, Juncus, and Alopecurus species

•Juncus balticus & J. ensifolius germination (61–73%) was highest after≥2months of cold, wet storage and incubation at 15–27°C.•J. tenuis and J. torreyi at 15–27°C had 51–58% germination both at the start of the study and after a year of wet storage.•For germination of Alopecurus aequalis and Carex nebrascensis, we recommend cold dry storage and exposure to ΔT=8–12°C that reach maxima of 23–30°C.•Juncus spp. germination did not vary significantly between 12 and 14h photoperiods. Factors affecting seed germination of select wetland and aquatic plants were investigated in two experiments. In the first, seeds of four Juncus species, Alopecurus aequalis, and Carex nebrascensis were stored overwinter at 3–4°C either dry or wet. In spring, these groups were further divided into four constant temperature treatments (15, 20, 25, or 30°C) and 3 fluctuating temperature treatments (low, moderate, high). In the second experiment, the duration of cold-wet storage, photoperiod, and temperature were further evaluated. In the first experiment, cold-wet seed storage led to higher and faster germination for all but C. nebrascensis; Fluctuating temperatures produced the highest germination of A. aequalis, C. nebrascensis, Juncus tenuis, and J. ensifolius. In Experiment 2, seed storage time effects varied with species. Photoperiod effects (12v. 14h light) were generally insignificant. Diel temperature fluctuations of 15–27°C produced higher seed germination than 32–38°C for all four Juncus species. The highest germination percentages of J. balticus (64–69%) and J. ensifolius (61–73%) occurred after at least 2 months of cold-wet storage and incubation at 15–27°C, whereas J. tenuis and J. torreyi had 51–58% germination both at the start of the study and after a year of wet vernalization. The conditions for germination of the species studied still needs further optimization, but the effects of temperature, temperature fluctuation, overwinter storage conditions, as well as the days to germinate at a given temperature, have been at least partly elucidated for the species studied. The data can now be used for initiating seed pretreatment for habitat projects.