Baby sugar watermelons are my favorite to grow. There are a couple of things to look for in a ripe baby watermelon. First, baby watermelons should weigh at least 10 pounds before picked. Also the vine will begin to die and turn brown at the spot where it connects to the watermelon. The spot where it was resting on the ground should have a yellow rine, not white, yellow indicates ripeness. Lastly thud the mellon with your finger, a hollow thud means it is ripe.