60-65 days. Watermelon Radish Seeds. Raphanus sativus. Non-GMO. Heirloom. AKA: "Roseheart Radish" or "Red Meat Radish". Watermelon Radish seeds are native to China and a cousin to Daikon radish. Watermelon Radish seeds quickly develop a Fuschia-colored interior, adding vibrant color to dishes and making a perfect root vegetable for pickling! Watermelon radish is an eye-catching and reliable seller at any Farmers' Market. ~2,500 seeds/oz.