Native plant establishment and competition with an invasive species on Georgia roadsides
Johnston, Christopher Ross
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Invasive species are a costly problem on roadsides in Georgia that require chemical and cultural control. Currently, agronomists manage invasive weeds with mowing and herbicide applications on grassy roadsides but alternative strategies are needed to enhance the potential for long-term control. Restoration through the establishment of sustainable native plant communities may be an effective alternative for invasive weed control on Georgia roadsides. Species selection, seeding timing, seeding rate, and location could influence the establishment of native species under roadside conditions and warrant further investigation. In field experiments, the native species blackeyed Susan (Rudbeckia hirta L.), indiangrass (Sorghastrum nutans (L.) Nash), lanceleaf coreopsis (Coreopsis lanceolata L.), swamp milkweed (Asclepias incarnata L.) and wild bergamot (Monarda fistulosa L.) had high potential for successful establishment on Georgia roadsides. Seeding of native species in the spring generally had faster initial establishment than fall seeding. Greenhouse studies indicated that Johnsongrass (Sorghum halepense (L.) Pers.), a problematic roadside weed, had a higher competitive growth than indiangrass during establishment. Mowing 60 days after seeding reduced Johnsongrass and indiangrass biomass 88% and 4% at 30 days after mowing, respectively. Results suggest that sequential mowing following regrowth may reduce the competitiveness of Johnsongrass with indiangrass.