90 - 95 Days to maturity. Citrullus lanatus. Black Diamond Yellow Belly Watermelon Seeds. Non-GMO, annual, open-pollinated, heirloom, heat tolerant, seeded, giant watermelon. This watermelon has red flesh with a dark blue-black rind and grows to be 30-50 lbs. The rind will turn yellow where it rests on the ground as it ripens. ~400 seeds/oz.