"Crimson Sweet" is a cultivar of watermelon (Citrullus lanatus), a warm, long-season crop that performs best when temperatures are between 70 and 85 degrees Fahrenheit. Crimson Sweet Watermelon Seeds. Citrullus lanatus. Non-GMO. Open Pollinated. Crimson Sweet watermelon seeds deliver one of the most iconic and delicious fruits To get a head start on the long growing season, start plants indoors 4 to 5 weeks before outdoor planting time. Crisp and sweet, medium-red flesh, mild flavor. A good producing type that is still quite popular. Full Sun. Sprouts in 5-10 Days. Ideal Temperature: 70-95 Degrees F. Seed Depth: 1/2-1 inch. Crimson Sweet. 88 days — The fruits are light-green with dark-green stripes and average about twenty five pounds. The flesh is dark red with a fine texture and very sweet