Abstract Seeds of southern seaoats (Uniola paniculata L.) were removed from storage in July 2004, surface disinfested with 2.6% sodium hypochlorite (NaOCl) for 15 min, and sown in styrofoam tobacco (Nicotiana tabacum L.) float trays (flats) filled with a vermiculite-based hydroponic substrate. Trays were floated in plastic tubs (one tray per tub) containing a complete nutrient solution with nitrogen (N) at 10, 60, 120, 180, or 240 mg·L−1 (ppm) from a 2N–3.5P–1K ratio (8N–32P2O5–5K2O) liquid slow-release fertilizer. After 10 weeks the study was terminated and data recorded. Total plant, top, leaf, stem, and root dry weights increased quadratically with increasing nitrogen application rate (NAR) with maximum dry weights calculated to occur with N at 140 to 150 mg-L−1, respectively. Other growth indexes of leaf area, root length, root area, plant height, crown growth index, tiller number, and leaf number also increased quadratically with increasing NAR similar to dry weight data. Leaf area, root length, and root area were maximized with N at 157, 140, and 140 mg-L−1, respectively. Root to top ratio and specific leaf area were both unaffected by NAR. Leaf mineral nutrient concentrations of N and phosphorus responded quadratically with increasing NAR whereas, foliar mineral nutrient concentrations of potassium, calcium, sulfur, sodium (Na), manganese, zinc, and copper responded linearly to increasing NARs. With the exception of Na and iron, foliar nutrient content for all analyzed nutrients increased quadratically with increasing NAR. Calculated leaf N concentration at maximum top dry weight was 31 mg·g−1. Southern seaoats can be grown successfully using the float system with optimum N rates of 140 to 150 mg·L−1 provided by a fertilizer having a 2N–3.5P–1K ratio.