Planting. Poor seed germination is the main problem with growing seedless watermelons. When direct seeding, the soil temperature should be minimum of 70 degrees F. at a depth of 4 inches. Soil temperatures below 70 degree F. will reduce germination and emergence. When growing transplants, use 12- to 2-inch seedling cells or peat pellets. Soak the planting medium thoroughly, and let drain 4 to 6 hours before sowing. Plant 1 or 2 seeds per cell or pellet. The greenhouse temperature should be 75 to 85 degrees F. during the germination period. Do not allow the growing medium to become dry, but do not over water during initial germination. Begin watering, as needed, after 10 to 15 percent of the seedlings have emerged. Plants should be ready for transplanting in 3 to 4 weeks. Transplants should have not more than 3 true leaves when set in the field. Use of older, larger transplants can cause slow, stunted growth and poor yields. In-row and between-row spacing is generally 48 X 80 inches.