Congo Watermelon Seeds. Non-GMO, annual, organic, open-pollinated, heirloom, heat tolerant, seeded, giant watermelon. Resistant to Anthracnose (1). Congo Watermelon produces sweet, red-fleshed melons up to 50 pounds! Sugar test reveals sugar levels as high as 9.5% Now that is a sweet melon for a hot summer day. Congo is sure to satisfy the kids' sweet-tooth and is a must at any picnic.