Seed size, abundance, viability, dormancy, and germination requirements strongly influence plant establishment and therefore are important considerations in restoration of native vegetation. These characteristics provide criteria for selection of suitable species, development of collection and pretreatment methods, and determination of seeding densities.
The first set of objectives of this study were to measure seed weights and test seed viability, dormancy status, and germination requirements for the species used in propagation by seed. The second set of objectives was to test seed propagation under field conditions and to compare the performances of different seed mixtures.
Our results suggest several guidelines for increasing the chance of successful establishment of native plant species by seed. These recommendations must be provisional, however, considering the limitations of this initial study.
• Sowing densities must take into consideration seed viability, with higher densities needed for species with lower viability. Viability among just the 9 species investigated in this study ranged from <10% to >80%.
• Seeds should be sown in the fall, so any seed dormancy can be broken by winter stratification. Three of the 9 species in this study had significant seed dormancy, which in each case was broken by stratification.
• Weed seeds in the soil seed bank are a major impediment to restoration using seed propagation. Effective seed bank reduction measures should be instituted before field sowing. In addition, sowing densities should be much higher than the 100-300 seeds per 1250 cm2 rates used in this study.
• Seed mixtures with several species should have greater success than monocultures.
First, a mixture that produces a succession of plants should be more effective in capturing the site against weed species. We recommend mixtures that combine species (like the annual Plagiobothrys figuratus) that have rapid initial growth with species (like Deschampsia cespitosa) that become dominant after the first year.
Second, year-to-year variability in weather makes it difficult to match species with their proper site conditions. We recommend that sowing mixtures include species suitable for the range of soil and hydrological conditions in wetland prairies.