Seed Dormancy Break and Germination for Restoration of Three Globally Important Wetland Bulrushes

Abstract

Limited knowledge of seed dormancy break, germination requirements, and intraspecific variation of these traits hinders revegetation of many species targeted for restoration. We evaluated the importance of cold stratification and chemical scarification for breaking seed dormancy and the impact of soaking in water on germination for three globally distributed bulrush species. These species, Bolboschoenus maritimus (alkali bulrush), Schoenoplectus acutus (hardstem bulrush), and S. americanus (threesquare bulrush), form critical habitat in Great Salt Lake wetlands. For B. maritimus and S. acutus, we also evaluated variation in response to seed dormancy breaking treatments among geographically-distant seed sources. We found that both 180 days of cold, moist stratification or 48 hours of bleach scarification were effective for breaking seed dormancy for most seed sources of B. maritimus. For S. acutus, longer stratification lengths may result in consistently higher germination percentages, but 30 days of stratification may be of sufficient length for some source sites. For S. americanus, stratification improved germination in one experiment, but 20–60 percent of viable seed did not germinate in each experiment potentially due to a poor understanding of germination requirements. Soaking seeds in water under greenhouse conditions, improved the germination of all species when done after dormancy breaking treatments. Importantly, response to dormancy breaking treatment varied among source sites; intraspecific variation may account for unpredictable responses to dormancy breaking treatments. These findings can assist practitioners in crafting strategies to effectively break dormancy and germinate seeds of B. maritimus, S. acutus, and S. americanus.