7-8 inches Click to see full answer. Furthermore, how big is an icebox watermelon?Icebox watermelons, including ‘Sugar Baby’, earn their name from their small fruit, which weighs in at 6 to 15 pounds and measures 6 to 10 inches across.Beside above, how long does it take for sugar baby watermelons to grow? approximately 75 days Keeping this in view, how do I know when my icebox watermelon is ripe? An icebox watermelon is ready to be picked when that resting spot’s color turns from greenish white to yellow or cream and after the rest of the rind becomes dull green. Replace the fruit on the ground in the same position it was previously if the fruit isn’t ready to be picked.How do you know when to pick a watermelon from the garden?A watermelon plant gives off a number of signs that it’s ready to harvest. Watermelon should be ready about 80 days after it is planted. At about the 75-day mark, start keeping your eye on it to see if it is ripe. The tendrils that are normally bright green near where the watermelon meets the stem will turn brown.