| Summary: | Flowering rush, Butomus umbellatus, has been an increasing problem in the Detroit Lakes chain of lakes for more than 45 years. Flowering rush dominates ecosystems by crowding out native species including hardstem bulrush, Schoenoplectus acutus; a vital part of native ecosystems. Furthermore, flowering rush creates boating hazards and hampers recreational activities on the lakes. The phenological differences between flowering rush and the native hardstem bulrush were examined as part of a project determining the best management practices for controlling this invasive species. Biomass allocation, plant height, carbohydrate allocation and reproductive structures of flowering rush were examined in the Detroit Lakes system. Flowering rush and hardstem bulrush exhibited similar times of emergence, maximal growth and senescence, requiring careful management to protect the native species. Hardstem bulrush was approximately one meter taller than flowering rush during mid-summer. Flowering rush continually formed rhizome buds as its primary mode of reproduction and approximately one bud per every two grams of rhizome, or 393 buds per m2, were produced within the midst of a flowering rush bed. This high density of rhizome buds may lead to further spread of flowering rush as well as long-term treatment of this “seed” bed. The number of leaves sprouting from rhizomes was greatest in mid-summer in both 2010 and 2011. Throughout the sampling period 84% of the biomass of flowering rush plants was found below ground, indicating treatment efforts will need to target a reduction of below ground material potentially over several years. Ryan Smith is a major in Biology with minors in Chemistry and Spanish from Zimmerman, MN. Jane Tolkinen is a major in Biology with a minor in Business and Chemistry from Baxter, MN. Jordan Kosminskas is a major in Biology and a minor in Chemistry from Blaine, MN. Nicole Lindor is a major in Biology with a minor in Psychology and Chemistry from Cyrus, MN. Jennifer Renner is a major in Biology with a minor in Chemistry from Audubon, MN. Casey Olson is a major in Biology and Environmental Studies from Rock Springs, WY. This paper was a part of a Summer Research Program. This paper was submitted for the Research Awards and Grants under Dr. Michelle Marko. The title of the grant is the Pelican River Watershed District, Minnesota Department of Natural Resources, Concordia College Fugelstad-Torstveit Endowment Research Fund, NSF S-STEM grant #0850132 to H.L.K. Manning.
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