Mesotrione is a proven effective weed control product in many agricultural settings but its use within a hydroseeding mixture has not been investigated. Two experiments were conducted to evaluate the effects of mesotrione rate (1) and duration of herbicide exposure (2) on turf establishment and weed populations. The experimental design of both studies was a randomized, complete block, with four replications. Perennial ryegrass (Lolium perenne L., variety not stated) was hydroseeded on an Antigo silt loam (pH 7.0) in July 2009 and 2010 at 39 g m^-2 in a slurry delivering 6.1 L m^-2. Treatments in the first study were mesotrione rates of 0.0, 0.02, 0.04, and 0.06 ml m^-2. Treatments in the second study were duration of mixture in tank before applying of 0, 2, and 4 hours, with and without a mesotrione rate of 0.04 ml m^-2. Turfgrass percent cover, turfgrass injury, and weed populations were assessed for both studies. Results from the mesotrione rate study were similar in both years. The addition of mesotrione at any rate to the hydroseeding slurry did not reduce desired turf populations; in many cases, the amount of desired turf cover increased. Weed populations were significantly reduced by all mesotrione rates; the effect was most evident at the two highest rates. No treatments caused turf injury. Results from year one of the herbicide exposure duration study were similar. The addition of mesotrione to the hydroseeding mixture for any of the durations did not reduce desired turf populations. Mixture duration did not have a negative effect on herbicide efficacy. No treatments caused turf injury.