Some tips for growing watermelons include placing them in a sunny spot, planting seeds only once the soil warms up and making sure the soil is rich in organic material. Watermelon plants also require well-drained and consistently moist soil.
To grow watermelons from seeds, wait until the soil reaches 70 degrees Fahrenheit before sowing the seeds, or transplant watermelon seedlings well after the last frost. Prepare the gardening site where the plants can have access to full sun and the soil is well-drained. Work several inches of compost or aged manure into the soil to enrich it and improve drainage, making sure that the pH remains between 6 and 7.
Plant the seedlings 2 feet apart in raised rows, keeping 6 feet between rows. Cover the seedlings with row covers until the vines start to flower. Add plastic or other types of warm mulch to the soil around the plants to keep the soil moist and warm as well as to inhibit weed growth.
Water the plants with up to 2 inches of water per week to keep the soil consistently moist, but avoid wetting the foliage. Once the fruits start to form, reduce watering. Feed the seedlings with a nitrogen-heavy fertilizer until the plants flower, and then switch to phosphorus- and potassium-based fertilizers.