Triploid watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] consumption is increasing in the U.S. However, some of the original problems, poor and inconsistent germination, still exist. Seeds of several triploid and diploid watermelon cultivars were subjected to a variety of treatments to improve germination. Control and scarified seeds, by nicking, were incubated at 25 or 30 °C in either 5 or 10 mL H2O or hydrogen peroxide (H2O2). Triploid seed germination was strongly inhibited in all cultivars when seeds were at 10 mL of the H2O or H2O2; both nicking and H2O2 increased germination, but not equal to rate of the control in 5 mL H2O or H2O2. Germination of diploid cultivars was unaffected by any treatment. Seed morphological measurments indicated that triploid seed has a smaller embryo with a large and highly variable (CV = 105%) air space surrounding the embryonic axis as compared with the diploid seed. These data suggests that triploid watermelon seed germination is not inhibited by the seedcoat thickness alone. Seed moisture plays a significant role in germination, emergence, and stand uniformity.