||Once covering more than 48 million ha in east-central Texas, blackland prairie has been reduced to less than 21,000 ha. Reestablishment is often difficult because of competition from
exotic warm-season grasses. We tested the efficacy of four post-emergent imazapic herbicide treatments for weed control in a completely randomized block experiment with three blocks. A
good seed bed was created using conventional tillage, and prior to seeding a single application of glyphosate at 2.2 kg ai/ha was applied to the site to kill any existing vegetation. At the time of
seeding, imazapic was applied at 0.2, 0.1, and 0.06 kg ai/ha to provide residual weed control. A mixture, using equal parts of big bluestem (Andropogon gerardii), indiangrass (Sorghastrum
nutans), little bluestem (Schizachyrium scoparium), and sideoats grama (Bouteloua curtipendula), was seeded using a J. Thom 42 WildseederŪ drill at a rate of 1.75 kg pure live seeds/ha. All three imazapic treatments had greater seedling density than controls across species. Plants in the low imazapic treatments showed greater shoot growth than higher rate treatments. End-of-season aboveground biomass for broadleaf species decreased in the imazapic-treated plots compared to controls, whereas biomass of native grasses increased with imazapic treatments. Biomass of exotic warm-season grasses that were tolerant to imazapic did not differ between treatments and by the end of the growing season were the dominant vegetation in all
plots. Percent native grass flowering was greatest in the medium rate imazapic plots. Our information shows the importance of using imazapic to establish the native warm-season grasses, but exotic bluestems prevented optimum native grass densities.