Plant density, species diversity, and the biomass of sedge meadow species were measured in mesocosms treated with one of two levels of four treatments in a randomized block experiment: stratified or not stratified seed, high or low groundwater level, high or low seeding density, and a complete set of all species or a split-set where non-aggressive species were seeded in the spring and aggressive species were seeded the following fall. The study was conducted at Iowa State University’s Hinds Research Farm in Ames, IA from 2013-2016. The high groundwater level had the greatest impact on increasing the plant density, diversity, and biomass of sedge meadow species. Stratifying seed also had a significant impact, but to a lesser extent. Seed density was found to have no effect on sedge meadow species response. The split-set of seeded species increased the plant density and biomass of many non-aggressive sedge species, but only a few grasses or forbs. The split-set also significantly reduced the number of aggressive species present at the end of three years.

In a follow-up study from 2015-2016 at the same research site, plant density and species diversity of sedge meadow species were measured in mesocosms treated with varying fine-scale groundwater levels and seeding dates. The groundwater levels were 0, 5, 10, and 20 cm measured below soil surface. The seeding dates were June 16, June 30, and July 14, 2016. The plant density of forb species increased by 0.6 plants/ 0.4 m2 soil surface / cm decrease in groundwater level (p <0.001). The seeding date of June 30 resulted in the highest average plant density of forbs at 6.9 per m2 soil surface (p <0.05). S. tabernaemontani decreased at the rate of -0.1 plants/ 0.4 m2 soil surface/ cm decrease in groundwater level (p <0.001). High numbers of S. tabernaemontani corresponded with decreased plant density of other species and decreased diversity.