 Seedless watermelons became more popular in the 21st century, rising to nearly 85% of total watermelon sales in the United States in 2014.Watermelons are plants grown in climates from tropical to temperate, needing temperatures higher than about to thrive.On a garden scale, seeds are usually sown in pots under cover and transplanted into well-drained sandy loam with a pH between 5.5 and 7, and medium levels of nitrogen.