Germination Timing and Dormancy Break in Seeds of Summer Farewell (Dalea pinnata, Fabaceae)

Abstract

Summer farewell (Dalea pinnata) is a legume found in upland ecosystems throughout the southeastern United States. Often used in seed mixes for restoration purposes, it represents an opportunity for the emerging native seed industry in this region. Yet its germination characteristics are not well known. Our objective was to assess the germination timing and potential dormancy mechanisms of summer farewell. We specifically addressed the following questions: 1) to what extent do seeds germinate after shedding? 2) do seeds possess physical dormancy? and 3) can germination be enhanced using dormancy-breaking treatments? Summer farewell seeds germinated to a limited extent upon shedding, and most seeds (> 75%) in the population were shed with water-impermeable coats, or physical dormancy. Germination occurred equally well in light or darkness. Remaining ungerminated seeds displayed a high degree of viability (> 90%) after one year of burial. Thus summer farewell seeds are capable of forming soil seed banks. Scarification followed by incubation at constant temperatures yielded high germination. Germination of mechanically scarified seeds was superior to seeds scarified in acid for 5 or 10 minutes and unscarified seeds. However, incubation at 35°C may be deleterious. We discuss recommendations for restoration practitioners and seed producers.