The favorite trick of thumping a melon to check for ripeness doesn't actually indicate whether the melon is sweet. Watermelon sugar content results from healthy vines, good growing conditions, sunlight and a long growing season. Creating those conditions gives gardeners the best chance at a perfect melon. Any watermelon can be instantly ruined by harvesting too early since sugar does not increase after picking. Checking vines as well as melons for specific signals clues gardeners in on the proper moment. Shoppers in groceries may benefit as well.
Select a watermelon variety known to grow well in the local USDA plant hardiness zone. Choose melons with high resistance to disease. Bush or semi-bush types conserve space, and small melons mature earlier than large watermelon cultivars. For best flavor, melons should ripen in late summer before average daily temperatures fall.
Till early in the planting season. Mounding soil in hills or in raised beds warms the planting zone and allows melons an early start. Direct-seed the hills or transplant melons started indoors when the soil temperature reaches a dependable minimum of 65 degrees F.
Fertilize three times during the growing season. Purdue University Extension recommends 1 to 2 tbsps. of 6-10-10 fertilizer per hill at planting time. Apply 1 tbsp. of fertilizer one week after blooming begins and repeat the feeding three weeks later.
Water and weed regularly. The water supply in the soil must be constant for steady melon growth. Competing weeds shade the leaves that manufacture sugar for the melons. Watermelon plants need long hours of full sun to fully develop high quality fruits.
Check individual melons for ripeness when the skin dulls and roughens. Lift the melon carefully to note the color of the shaded section resting on the ground. Ripe melons shift from white to yellow on the underside when mature. Tendrils near the stem of ripe melons shrivel when the melon reaches maturity.